The problem with D3 is the utter failure to tie damage with mechanics. Did that molten mob just run through you? Sorry, you're dead. Proper mechanics should be like the Belial fight. Give players visual cues, and more importantly the chance to do something (as opposed to equip something) to mitigate incoming damage.
Because the mechanics in D3 are so bad, we've had to resort to just stacking life, armor and resist. It's the same thing with DPS. Since all the proc stuff is severely gimped, we're reduced to stacking cc, cd and asi. The end result of all this? Combat is reduced to utterly boring tank and spank affairs.
Trying to simplify things was the worst decision JW ever made. Complexity is good. Complexity makes things interesting.
I agree completely regading mechanics and have been saying it since Beta. The changes to Damage Reflection were a good start.
On the other hand - I disagree regarding complexity. Complexity on it's own is not a good thing. Far too much of being good at D2 involved knowing how silly arcane little systems worked and being penalized for experimenting and making mistakes.
You can have a game that is simple to learn and hard to master, and be amazing. IE: The difference between SC1 and SC2.
First, I agree with the quote inside the quote (Inception anyone?).
Although Blizzard did add these visual cues or attack animation in which a rockworm pops out of the ground or a fallen commander (?) jumps while swinging back his sword for a massive strike, I find that the little damaging attacks are a bit too damaging in some cases. Take the molten example: before being nerfed the molten trail was dealing a ton of damage, after the nerf it's a bit fine. A constant aoe following an enemy should deal very little damage as it is aoe and constant. The molten explosion however can be dodged and "charges" up before exploding. High damage is fully understandable here.
The plagued affix however has been buffed to deal a bit too much damage and it also stacks which is deceiving to the player. If anything the plague pools should deal little damage (constant aoe yes?) and perhaps have the monsters surrounded by a cloud of infection gases and flies or something which would be another constant aoe damage. So two small damaging things but if you are in a plague pool and the enemy is near you the damage would then add up. If the poison aura is too much like molten it could perhaps be a periodically spawned poison cloud which slowly drifts around randomly before disappearing dealing constant aoe damage (small amount of damage).
Visual cues and traps should deal a ton of damage (act 3 fire wall has no cues and should be fixed to have one - act 1 cleavers should deal a lot of damage). Normal attacks should deal less damage, enemies that just
deal normal attacks should either have more life or be in greater quantities to swarm around you.Complexity:
This depends on what is being made complex and how much complexity is being added. Skill runes is an illusion of complexity where only 1-2 of the runes are chosen while the rest will never be used (in most cases).
When it comes to dealing damage we only have two options. Black (non elemental) weapons with elemental % added or any of the other damage types. Diablo 2 we had proc on hits which actually did damage such as crushing blow, chain lightning and so on.
Skill Tree vs. unlimited skill respec. Both are good but the latter kills replay value in the game. Their is no point in saving gear for another barbarian since 1: you can change your skills and 2: you don't want to make another barbarian when you have one at plvl 30 or something.
Skill Trees can be annoying only when first experimenting on a new build (in which the build may be horrible or you mess up), or if the skill itself is badly designed. Having no respecs can also be a bit frustrating if you character isn't working out. Both skill options have their up and down sides imo (I like Titan's Quest's dual mastery in this case - though TQ had some issues as well which mods helped).