The first half of the early game (which is arguably the most experienced part by the overwhelming majority of players) is much improved.
Halving all the xp penalties was a good move, and I also got the impression that the early loot is a bit better and more abundant with some more initial weak randarts.
So the early game is now more enjoyable because you can get a new character up and running faster and start gearing it up and aiming towards a build.
The second half is also good, but some bad difficulty spikes begin to appear.
Some early chests and vaults are generating some OP elites (for the early maps) and in some cases some nasty uniques. Compared to 1.5 this seems to have been increased.
For instance, in the old forest I actualy got the same vault generated 3 runs in a row: it spawns two lv 25 elite worm casters that blighted/diseased my ass to death.
I think a good compromise here would be to have a different message for these stronger chests/vaults: warn the player and let they know that this particular vault/chest is nastier than normal. This maintains the challenge while giving the player better agency if they want to approach it or not, instead of it being just a cheap RNG shot as it is now.
Regarding the bosses which all got buffed up, they really feel like a difficult boss fight now which I think is fine, but... in the same spirit of the idea above, I think the player needs better warning regarding them and specially regarding the early bosses like the bandit lord and high tempest.
I know that Urkis is already an infamous newbie eater but baiting these players who just reached lv 14 into following that questline is bad design imo, but even the bandit lord got me by surprise on my first 1.6 run, but also that pregnant necromancer in the mausoleum. They are more difficult now and more worthy of being a boss so their fight are more enjoyable, but the player is not being warned well enough on the danger, specially when those quests become available or even "forced" in the case of the bandit lord.
In the same spirit of the suggestion above, I think warning the player in a more clearer way that the coming fight is harder than usual would be best for all the bosses.
Mid Game (lv20~40): Good improvements
Not much to say here. The mid game continues to be as strong as before. But given how fast the early game goes by now, the mid game where your build starts to shine has become more enjoyable too as you reach it faster everytime.
Altough some of the same problems affecting the early game are also at play here: The weird spikes regarding the uniques spawn table coming out of vaults/chests. But with more points in a build the player at least now has some tools to deal with those spikes.
In the Sher'tul base we have a handy tool to test our damage output. It would be nice to have a turret that the player can configure to do a certain type of attack, to be able to test our defenses. So we would configure the frequency of the attack (1 per turn, 2 per turn, 1 every 2 turns, etc), if it's melee, ranged or spell (to test defense against projectiles) and the attack type (physical, nature, arcane, etc) and finally a basic value, so for example a ranged attack of 100 cold shooting every turn at the player. This damage of course would be non-lethal.
Late Game (40~50): Some minor improvements, but its still a grind
I already had a dislike for TOME4's late game which is almost entirely due to the prides design.
By this point in the game, one's character build is already in full operation or close to. If the game wants to put my build to the ultimate test that is fine, if I already cleared 1 room of a Pride why would I have to grind trough TWO COPY PASTED more rooms? They offer no new challenge for my build to overcome that I didn't already encounter in the 1st screen of a pride location. So it becomes just a mindless grind.
Now compared to 1.5, the size of each pride map has been somewhat reduced which is good. Also they now have better different tiles and layout which is also very welcome. But I still think 3 maps per pride is too much. Two maps per pride would already be a great improvement, and if that 2nd map became some sort of unique area like some sort of arena for each of the pride leader then it would be great and something that I look forward to, instead of the current "eugh here comes the prides again, let me just blink/teleport/run straight to the 3rd map even tough I'm obliterating everything already with 1-2 skills because grinding clearing through these is just not fun".
For high peak:
It is in severe need of unique/interesting layout generation and unique tiles like what was done for the prides. Because as of now my algorythim for it is: 1) find/go straight for the stairs to the next level, kill the stupid unique guarding it, reach next level, repeat.
Yes I could grind the vaults for randarts, but at this point the vaults also become annoying:
1) Nope, if I see that the vault require even 1 tile of digging, I'm out. - digging in general what an useless feature (The stats/effects on pickaxes are welcome tough

2) Nope, if I see that the ground is lava I'm out. Yes even if I have capped fire resistance I'm not - walking tile by tile watching those zeros go up like a stupid drem when I'm a - shalorem archmage chain bolting bastards for 2k of mixed arcana fire cold lightning damage with my awesome ring. It's just a waste of time.
Oh and why the epic music only for the slime tunnel? Make it play on repeat during the entirety of high peak including the last fight and then I'll at least have an excuse to stay there for longer.