Per request of many people i decided to write down a guide on Sentinel class. Ill try to list useful tips and tricks and in the end ill include 3 builds which performed exceptionally on the ladder this patch. Taking wave 511, 395 and 365 and those numbers are not the limits, they can go way higher with more dedication and items.
Skills 
In this section ill describe best methods to survive, there is no problem with dealing damage so your safety always comes first
Vengeance
Bread and butter for any melee or close ranged build. As a support skill it provides you 36% less damage taken (not only from hits, but from dot’s too) , 100% damage buff while preparing for riposte, free void charges from “essence of revenge node”. The only downside is that you have to include it in your rotation and hit every 2 seconds for buffs, but imho if you get used to it you get so much tankier than other sentinel builds.
Lunge
2nd absolutely busted skill +100% void+elem prots, 4 str and 60% armor…Looks decent but not too strong right? the thing is you need to take 2 charge node and all CDR nodes which will make it 2 sec cd and the buffs stack so you get DOUBLE the initial bonus. But you shouldnt stop there if you have a slot for cdr affix on helm and your cd will be 1.6 sec, which will make you have triple bonus sometimes for short amount of time.
Ring Of shields
Good skill on any mastery but its godlike on Forge guard, my shields could tank 300+wave mobs on level 100 due to “shield crafter node” since even if they die…you will proc more from getting hit. Now the main trick to keep them alive is Sigils of hope skill! Sigils can give Healing effectivness to allies, so you can give 100%+ healing effectiveness to shields, doubling their healing you can also go for “eterra’s path” unique boots to tripple the healing, making them unkillable. Just go for 5-8 shields , max healing and 16 sec duration, CDR helm also helps.(the important part is not taking the node that doubles health regen otherwise they wont get this bonus!!!)
The other way to use it is to get short 4 sec duration 100% block when activated, but you will need >75% base block chance which easy reachable even on VK.
Volatile reversal
Very underestimated skill, but extremely strong even considering that main damage passives on it dont work due to bug(the pasives that make enemies take more damage)! imo there are 2 ways to use it 1st: go for no life replenish and use it for mana sustain, the other way to go both no life or mana sustain, but you will get 2 sec cd, why is it good? cause you are becoming Kiting GOD with lunge+volatile reversal, example in this video : Guide VR trick - YouTube . Always take attack speed node and the node that makes you travel +2 sec back in time. This buff stacks !!! so especially with 2 sec cd version you will have +72% attack and cast speed which is absolutely bonkers on any build. Be careful with it against ground Dot’S so that you wont teleport in your death!!!
Sigils of Hope
Very strong for almost any build (except void aura hammer throw). Gives whatever you need the most. Imo the strongest node is “iron sigils” which gives 250 armor per sigil, making you have enough armor and with more investment you can use “Urzil’s Pride” unique armor for 20-25 mana regen per second as I did on 2 of my builds.
FG or Pally (Vk WIP )
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Forge Guard
Many people underestimate this class, but its the best class to push arena among sentinels now, first of all he has 30% conditional damage reduction which comes handy sometimes, secondly his passives:
- The strongest passive is “Infinite bulwark” which provides 200% armor and pot find chance. with this you can tactically layout pots all over the arena and you will have enough to get through toughest enemies with them. example https://imgur.com/a/Mql53RX . Since we have pots you can shamelessly abuse strong affixes +800 dodge for 4 seconds after drinking potion and +300% ignite chance. Just get 5 potion belt and you will sustain buffs even during long fights.
Note for devs: This many pots are just for showcase, in reality you get way less especially on melee build since you accidentally pick up most of them while fighting. So its pretty balanced now, considering you have to invest 10 pts into it. - The second strongest passive is “shield crafter” 4% sounds not very strong but trust me its quite a lot because of trash mobs that hit fast, i usually step inside some bombard attacks from ice mages or necro chimers just to proc more shields.
- his damage passives are very strong: “retaliation” gives 150% inc damage and “Tide of battle” gives whooping 300% damage. As for how to effectively use them without dying: basically you need to be hit but not too much. If you use ring of shields i would recommend going for 5-7 shields this way you will get hit consistently, if you go 8 shields you will never get hit except for dangerous aoe. The other way that i found more efficient is Dodge, get a t5 belt with >+700 flat dodge you can ignore trash with good gear(but its expensive option!!) for starters use RoS and block! To use “tide of battle” you need to drink 2 sec after taking damage, here comes handy Fg racial passive: as soon as you see stacks of it going up you press pot, because you got hit (every 4 sec) and you get +300% damage. The important part that it is GENERAL damage so anything benefits from it, you can use any type of flat damage, you can do ignite, spells…everything will be decent with +450%.
- [edit 1] As I forgot to mention, Regenerator passive is also a good tool for sustain, if you go high prots and low hp it is better than Leech and can heal you up to 400 hp per sec(or more). Use it with fast hitting attacks or Devouring orb with Cataclysm or Abyssal Emission or anything that does many hits per second.
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Paladin
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judgment.
I have not seen people using at all, but imo its one of the strongest defensive options for paladin, use it as healing 5 second aura and you get 400-600 heal per second. This also enables you to use “Prayer” and “divine essence” passive for more buffs. especially effective against poison garbage which is number 1 enemy of any melee class in the game. The judgment tree pic will be added at the end in pally guide. -
Holy aura good overall skill that provides attacks speed, defenses and explosions use whatever you want. Use CDR helm for more uptime
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If you have block use 1 or more points into “Holy Symbol” passive, it counts as heal and can activate “Prayer” and “Divine essence” passives. Other strong passives are:“Holy Precision” “Reverence of Duality”, “Faith Armor” and “Light of Rahyeh” for fire builds.
Overall Pally has a bit more damage on some builds due to crit passive(shield throw) or ignite chance(rive ignite build), but lacks defenses compared to FG. I recommend this class for people who started the game with more gear and player skill FG will overcome pally. Pally is on par with FG in defenses if he uses vengeance as main spammable skill so that you will never run out of riposte reductions(you get -30% dmg from riposte hits, and you get 2-3 riposte per attack)+Judgment, this way he will have more sustain against poison and will have higher prots due to divine essences
Block, Dodge and RoS
These 3 mechanics sounds different but in reality they do the same thing : mitigating you from getting too much hits. It is important to have 1 or combination of 2 of these, because otherwise you will die to hordes of mobs even with high damage mitigation. But remember these are RnG mechanics they wont make you immortal even if you have 80+% block and 60%+ dodge and RoS you can still die if you have low damage mitigation or not careful. The best defensive mechanic in the game is movement speed learn how to sidestep dangerous attacks, learn how to approach each type of enemies, learn the weaknesses of yor build and which mobs are dangerous for you.
Ring Of shields
The easiest to access. Good for leveling and new players, read more in Skill’s section. It can be used for 2h weapon builds since they rarely have good block. If you are 1h go for block+RoS and you’ll be very tanky
Dodge
Very hard to build on items manually so it is an endgame option if you can pick up FG passive Infinite Bulwark and get a t5 belt affix dodge on pot. Sounds not reliable? In reality it is very decent, just pre-pot against situations that look dangerous and you are good to go, with 5-10 pts in Bulwark you wont be bothered by lack of potions. Very good endgame option with good gear, so that you wont need to invest into block or specialize into RoS.
Block
Many people and I myself probably made a mistake of going as much block as possible. This is wrong, you can do it ofc, but imo getting 60-75 solid block is more than enough for any build. Craft a good shield with t5 block chance and you already have 46%+ block, get 14 pts into block (5base+5 pally+4 FG) and you have 60% which is enough to deal with trash. Try to get high block protections on shield base and if lucky Idols with block prot. Without investing all points in block passives you can get more damage, protections or utility , depending on what you need.
Builds
Abyssal echo Jugg (770 waves patch 7.7)
Link to passives and skills: https://imgur.com/a/rJxb6HT . Core items: Oracle(not Sorcery!!!) staff with t5 mana regen, Sunforge helmet, Urzil’s body for mana regen, stack vit and prots on gear no need for t5 movement speed, t3 is enough. Oracle amulet with t5 %necro prot is very good addition. Gameplay on high mono: 80 mono - YouTube
For idols go 4 20%+ mana efficiency for void spell idols, additional slow and time rot would be useful but ideally youll have 1 slow+3 void prot affixes.
In patch 7.7 they finally fixed the enemy debuff node, so we got a bit more more damage! Also Sunforged helmet really helps to cover necrotic and poison protections gap.
Dangerous enemies:
- Chimera’s, necrotic whisps and soul spear user: since sentinel mathematically can not have high necrotic prot even with rare amulet and sunforged helmet they are deadly, avoid as much as possible without stopping spamming lunge/vengeance, remember as soon as you dont have vengeance or dodge buff you are as good as dead.
- snow wolves…never charge into them or they will one shot you. charge in other packs and wait till wolves die cause they are blocked by other enemies
- all dot shit, ice dudes that throw snow vortexes are very annoying and do lots of dps, poison is awful avoid all poison projectiles and pre pot for dodge
- beetles and Osprix vanguard can be dangerous cause do ridiculous damage which is hard to avoid. Always sustain all your buffs on and pray to survive, stacking pots on arena helps ALOT
Forge Guard minions (358 wave , patch 7.7)
Yes you heard it right, it is a minion Forge Guard build that did 350+ waves, you thought manifest armor and forge strike swords are utterly useless…well its not. Cause now we have REFLECT! Another meme? well…core of the build is:
You need 4 of those to get 100%+reflect on minions. Next you can do a quick math: what happens to a beetle that hits for 2k each of 30 weapons that reflect 100% damage and have no protections…correct beetle gets 60k UNMITIGATED reflect damage and dies one shotting herself. As for skills you just spam forge strike and refund mana with Volatile reversal, it takes a lot of training to do it, but you can do it 
In 7.7 they added annoying focus mod, thats why we are using manifest armor cause he is awesome for taunting. Stack as much minion hp as possible, get 2t5 minion dodge affixes fro 40-50% minion dodge and eye of reen is good for a small solo target dps boost. Stack as much protections as possible, but without Orian’s eye unique amulet its very hard, we really need it without lunge. Build link: https://imgur.com/a/W2Xw2ia
Imo very good build and definitely can go at least 600, but as any prot build you need op gear to climb high.
Vengeance pally (395 wave in 7.6)
7.7 update. Build had some serious nerfs. First of all with adaptive damage change from base spell damage we deal 30% less damage from explosions and the idols were nerfed so now we have 60% max proc chance, but its still very solid
The funniest build i played, skills and passives : https://imgur.com/a/KU4Q6O7
The build is not level 100 (on other builds i pushed arena on level 100) and still needs gear. the core of the build are idols, without them your damage will be much lower and build will be almost unplayable. You need idols with this prefix : Increased Area of Void Cleave - Item prefixes - Last Epoch Item Database it procs Holy aura much more frequently and the higher % you have the stronger it gets. then get divine scepter with t5 attack speed, other gear crit avoid, and all possible defenses like prots and glancing blow., Urzil’s pride for mana sustain and CDR helm for dps.
gameplay: Pally V build - YouTube
Tip: Target tough enemies first and leave trash around so they will proc counter attacks to increase clear speed!!
Shield throw (356 wave in 7.6)
7.7 update Same nerf as holy aura, with adaptive spell damage you just deal less damage, but the build is still viable
Made this build for memes, since you have 80%+ block and 67% dodge get good belt and 2 dodge% affixes on gear(body+boots) then enemies will have 6% to hit you without block or dodge, and if you learn to avoid one shots you are exceptionally tanky. Key items are keen idols that proc smite, which deals high damage and grants 50% attack speed. use wand for high base spell damage, craft %throwing speed on rings and gloves, my FG got >219% throwing speed on this build with Time reversal which is more than pally with holy aura activated! main tip: Use future strike node for 10 points you have 100% chance to inflict future attack, this thing can also proc smite, which makes the average amount of smites per hit =0.96 so almost 1 hit 1 smite. Link: https://imgur.com/a/TNA4zCO
Summary
Sentinel is the most fun class to play imo, it has many short term buffs that make you very strong but without them you can die easily on high arena. Builds are fun to create and require skill to play.
and its needed for shield crafter anyways.
if i manage to gear it up before 7.8