Perhaps not being one of those people that are “used to” hardcore/grinding RPGs and prefer “slow death with sloppy mistake somewhere” rather than a “surprise death”, but regardless, have a greater set of ideas that I think would be somewhat notable to take a look at
1st things 1st - I used to play a Masochist mode character (yes, pre-Beta) and yes died a lot until made that particular character a beast and then only few things could kill as well
Point/s being the following:
The Masochist mode only thing that really killed was hitstun, I can see how there’s a huge upgrade and a huge focus in items that give large amounts of “Stun avoidance” category but NOW, when you have an item like a Cloak with 500+ Stun avoidance lol, seems like that might not be as much of a problem 
Regardless, the big topic (Elephant in the room if you like) is the following:
AOE rules everything, not enough mobs can stand “toe to toe” with the player to survive the “initial” (actually more like spammable 100%) AoE, and 99.99% of stuff die before they even manage to raise an extremite to make a swing (partially could be the fact a 2 hand weapon for 99% of the time but still), either:
A - Everything dies with AoE
B - Things that survive the initial AoE can’t even penetrate the “exterior” (i.e. in case of mage the Ward) until hit again with the same AoE, yet alone do damage to HP
C - Things that aren’t in either of those 2 categories feel “clunky” and “slow” and “game stoppers” (for the most part, big brutes require to either skip and treat as environment hazard or spend 2 minutes fighting on that one mob), and finally
D - Cheap death (fast stack of “subsequent” damage) is the real player killer
About that a bit later but first want to point out a couple of (IMO) huge imbalances:
I might be only me but I really struggled with the Rogue probably/mostly compared to pretty much everything else. Even most recent example - don’t see how there should be a greater damage efficiency (and sustain per hit) from an ability like “Mana strike” with just a couple of nodes investment, but Flurry with almost max sustain (as much as earlier game level can give you) doesn’t even begin to compete lol
The mage hits with a 50-60 per swing dealing FULL AOE with one swing whilst the Rogue does like 15-25 per hit with 3 times the rate of hit but being able to hit only 2 guys at a time (lol)… Wand hits ALL the opponents in a “stack”, whilst the Rogue hits only a couple (or so it seemed to me tbh)
Perhaps the Mage is OP ?, perhaps the Rogue is underwhelming (think the latter is more accurate though tbh)
Now, as progression goes, there are really only few places that REALLY can kill you super easily (if not paying the attention)
1 - Ruins of Welryn (not the physical tripodas that hit like a truck, no, the real damage comes from those “purple blobs” on the ground that sometimes can’t even be seen, 3 on one spot on top of one another = poof, gone)
2 - Same thing later on, almost super smooth until the Temple’s entrance (i.e. Courtyard) where there are like 5-6 Void Clerics and you can see only a couple on the screen, again - some purple globs that can’t be seen = poof, gone
3 - If that is passed then the next first place to get killed is at the Saphire/Ruby/Emerald/whatever quarters, those guys that launch quite a few parabolas on top of one another in the same spot, the timespan between being hit by the first glob of damage until the last in the last one hits is like 0.75 of a second
4 - Again, smooth sailing (for the most part, depends on whether or not the Arbalests deal significant damage to you) up until the Heoborea boss (the tall spiritual/mana tree guy, the “rapid taps” on the ground that take like 25% of your HP per hit each in a quick succession)
5 - Nerf the Flayer sharks (haven’t gotten there yet now, guess a Cloak with 500 stun avoidance would do this time), and perhaps the last act green Nagas that come diving out of the ground always “facechecking” you, but in general - buff some mobs earlier at the expense of the “very few” that are real player killers (should provide a better playing experience overall IMO)
So, that’s my initial feedback (keep in mind, not just the last few days but have some experience from before, including masochist mode)
Now, onto the Suggestions:
1 - Don’t always make “trash mobs” trash, introduce here and there some “member of the pack” bonuses… Could be things like: +x damage per pack member (or pack member missing), +x regen or HP per pack member (or even per pack member missing), +x movement/attack per pack member, e.t.c…
The goal here is to not always reward AoE builds, make them less trashy and make at some particular cases/times a “kill 1 by 1” approach more rewardable (or at least more rewardable in initial impact)… Cause again, 99% of the time AoE rules, as is - the game is revolved around “sweeping” rather than focused/strategic combat tbh
2 - Introduce 1 new type of affix for elites: Duelist (deals more damage when away from allies, i.e. dueling only the player), this could be one more way to reward some of the “single-target” kill approach
3 - Introduce 1 new armor type (Subsequent damage reduction), should be focused around reducing “subsequent bursts” of same damage type (i.e. the stacked globs I mentioned from before)… I mean sure, goes against the “get more resistance bro” but I’d also suggest to reduce the overall efficiency (and dependancy) of resistances as a stat, i.e. cap it earlier at 50% and then reduce the elemental damage output by some portion (still enough to kill fast but not just because of resistances but cause of not having sustain or other defensive stats like lack of sustain or subsequent damage reduction)
This could also help to add for/against DoT (not just in PvP but against mobs), and then if you’d like also introduce a real DoT factor in the game, not just blobs (or fumes) of poison that come out of a slain monster
4 - Don’t be afraid to “piss people off”, reduce the number of mobs in game (i.e. reduce the “XP sponge” factor in the game), but make them trickier/stronger (even in non Maso mode), force the player to use some extra potion they didn’t think was necessary in fights that seemed “harmless” before they occurred
And finally the class balance change that my (so far) experience leads me to conclude that:
5 - Buff the Rogue, make the game revolve less around AoE attacks at least for the majority of act 1, or at least give more utility for strategic use… Like fore example one of the simplest changes I could suggest is simply have the Ballista also block terrain on it’s path (so it’s not just only an additional damage source but a somewhat-strategic asset for survival if correctly used)
That’s it (for now), perhaps might come up with a few more ideas later