So, this will be a pretty long post but I’ll try to stick with the characters I used to play a lot and stopped playing and why I stopped playing them. Sometimes they got nerfed too hard, sometimes I simply got bored of them. If you used to play a character for a long time and stopped, feel free to share your thoughts. Also, some people stopped playing certain characters after a nerf while others kept playing them and improved on them to counter those nerf (or you tried to counter them but failed because the nerf was too severe). This would also be a great thing to share as some people might have dropped their favourite character which can still be playable with certain changes in passives, skills, equip, etc.
So, let me start. I’ll try to explain what I liked about a certain character and what made me stop playing the character (sometimes completely, sometimes I still play them but not nearly to the extend I used to). By the way, I’m going to stick to characters I played over lvl90 for now but might share my thoughts on other characters I dropped before reaching that level.
1. Disintegrator (Sorcerer)
This was my first character iirc and I played it pre 0.8.2 and dropped it after the bugfix: “Fixed a bug where Disintegrate’s Twinbeam node caused other nodes such as Galvanized Defense and Lucomancer to apply their effects twice.”
I really enjoyed playing this character (I mean who doesn’t like beams?) as it was very tanky and could also deal very good damage. It was one of the strongest builds back then and I think a lot of people played it. The bugfix of course was one of the reasons I stopped playing this character but only in combination with the playstyle of it. You have to stand still to get your damage in which wasn’t too big of a problem pre-bugfix but it became a real pain, at least to me. One of the things that I enjoyed was the fact that I could tank a lot of things (of course not everything) but after the bugfix that changed and with a character that needs to stand still AND ramp up the damage, this became very unpleasant to play for me personally. I also didn’t really like the fact that Disintegrate is basically a gimmick and the real damage came from Lightning Blast (this “gimmick” thing is a recurring theme in many chars that I feel like should change, Warpath would be another example). I would have prefered to have Disintegrate as my main damage source, but a “pure” Disintegrate build just has too many weaknesses in my opinion. But because of the tankyness and damage pre-bugfix I could overlook that. If you are hardcore beam fanatic, please share your experience with this character because I 
BEAMS!
2. Static Orb (Sorcerer)
I think this was my third character and I played it before the skill got changed (in 0.8.3 iirc). When leveling my Disintegrator Mage I tried out Static Orb and to be honest I hated how the skill felt… but I liked the visuals so I decided to look into guides and give it a try and damn did I enjoy this character! Felt way more dynamic than the Disintegrator, obviously, as I didn’t have to channel to do damage. Because I used the Static Ground version (at least I think it used to be called static ground too back then) I could kind of pre-fire when enemies were charging me to get the most damage and not just namelock and the skill homes in and does all the work for me. I actually had to think about where to aim my spells at. The damage was very good and the skill felt extremely statisfying. The reason why I dropped this character is pretty obvious. The skill changed and even tho I tried many times I never found a new Static Orb build that I really enjoyed. Not to say the skill is bad, it’s just that I personally don’t like the new version, for me it lacks the excitement and impact the old version had. The Scatter Blast variant was pretty fun for a while but it got nerfed for some reason (at least the version where you use Static Orb as your main skill).
3. Devouring Orb Autobomber (Void Knight)
This is a character that I kind of love and hate at the same time. I love the fact that there is a lot going on and you can clear echoes pretty fast. It’s pretty safe too. It might be kind of weak against bosses but that never really bothered me too much. What I really dislike is the fact that you can play this character as basically a walking simulator. Put your Devouring Orb and Anomaly on autocast and have fun. There are a few chars like that and I personally don’t really like that. It kind of feels like my character is just an accessory to the skills and not actually the one doing the damage if that makes sense. I know some people enjoy that playstyle (like RF characters in PoE) but I enjoy actually doing something (even as a Necro 
). That’s why I use both Smite and Abyssal Echoes with my Autobomer so I actually play the game to some extend. But in the end what really made me stop playing this char is the whole stutterstep thing. Even with a lot of castspeed it feels weird. So very good char that I didn’t drop because of nerfs or bugfixed but simply because of the way it “feels” to play.
4. Hammer Throw - No Smite (Paladin)
Another char with a skill I hated during leveling but it felt interesting enough to try and make a valid character (pre 0.8.3). This character dealt all the damage with Hammerthrow (I got a Hammerthrow Smite Paladin too but they are vastly different characters with different playstyles!). This character was pretty tanky, relatively safe as a ranged character, could clear echoes very fast but struggled with bosses and to some extend with sustain via life leech as there are not that many sources of life leech for throwing characters. The main reason why I stopped playing this character was because I felt like I “finished” the character. Remember this was pre 0.8.3 so pre Julra and Legendaries. Also, it is a very simple character. There is no way to “combo” into anything like a big damage burst against bosses or something. Don’t get me wrong, I like simple and honest characters a lot, but they can sometimes become pretty boring after a while. It would have been nice to have some situational skill or something that adds a little excitement, as long as it’s not too much and I need like 4 skills in a specific order to buff me to do any damage to bosses (yeah, looking at you HoA! ) because that would have made it too exhausting to play which would have bored me aswell. So again I didn’t drop this character because of any nerfs or something, it was a very fun character that I played a lot but after a while there was no excitement anymore, it just felt done and “finished”, so I moved on…
5. Abomination (Necromancer)
I honestly didn’t play this build a lot but wanted to try it for the memes and boy what a meme that character is!!! I actually feel like Acolyte as a whole is just one big meme and I avoided that class for so long even tho my favourite character in Diablo 2 was the Necromancer.
I played a version where the Abomination does not decay and it was my only minion. Unlike the Manifest Armor Forgeguard (which plays like absolute dogshit) this character was pretty fun. Even tho the Abomination is just a pile of dead meat and bones it’s f-ing Einstein compared to the Manifest Armor which would rather do ice scating along the enemy than attack them. So why did I drop this character? It’s very strong, pretty safe and tanky and absolutely shits on bosses while still clearing echoes comfortabely. Easy: Snapshotting! Yes I know it has been discusses many times but it wasn’t the potential power creep aspect that bothered me but the fact that I had to respec two skills everytime I wanted to play that character. I didn’t change my equip when summoning the skelletons even tho I could have and the character still felt strong (or rather the Abomination felt strong and tanky) but always respeccing was just to annoying. First world problems but who cares… I want to hop in and start playing the game and not do chores beforehand.
6. Flurry + Multishot (Marksman)
Okay so this thread already took way more time to write than I hoped so I’ll try to make this one quick: I had 3 variations of the Flurry Marksman (Phys, Poison, Bowmage) and the Physical one was by far my favourite character back then. I think I started it in 0.8.3 or maybe 0.8.2 and it was my first character to get to lvl100. It was by far the smoothest playstyle of all characters I played and I got to lvl100 without really trying or actually noticing. Time went by so fast playing this character. Even tho I never managed to beat T4 Julra with this character (Dodge char with pretty low health) I still had a blast with this char. The reason why I dropped it (and the other 2 variants) should be no surprise - 0.8.5 happened and they got shit on so hard it actually feels just sad.
7. Poison Flurry (Bladedancer)
Created the character in like 0.8.2 or something.
Played the non-channeling version and didn’t like it because glass cannon.
Then 0.8.4 introduced Umbral Blades.
Loved the skill and changed from dodge based to glancing blow.
Died too much because glass cannon and shitty sustain with throwing attacks.
Then, like 2 or 3 weeks before 0.8.5 hit I respecced back into melee channeled poison Flurry and tweaked it a bit.
It was like taking crack (or at least that’s how some people would describe it).
Absolutely loved it, even more than my Phys Flurry Marksman.
Pretty much exclusively played that character during that time because I was having sooooo much fun with it!
Cleared echoes fast, simply annihilated bosses and I really had to play the game!
Because it was still a glass cannon I actually had to think about what enemies to attack first, where to shift, when to stay back and wait and actually dodge stuff! Felt great and very rewarding!
But then the weird uncle 0.8.5 came around and you know… R.I.P. that character… 
So there are many more characters I could write about, but I wanted to stick with those 7 for now because damn this took a long time to write!!!
Please share your experiences with characters your played a lot but then dropped for some reason, even if it’s just “because I got bored with it and wanted to try something new” because that too is a valid reason and, at least in my opinion, usefull input for the Devs. 
Most of the builds I’ve played aren’t from the forums so I don’t know or remember the names.