Stats

[Lissa]

So unless I'm missing something obvious, VIT is always, by far, the best defensive stat and DEX is the worst, by far. This seems odd to me that there is so much difference between the various stats. I suppose if you assume some leech adding in health return, then EH and DEX will look much better, but still DEX doesn't seem to be able to hold up to EH at all. Please check and correct, this can't be entirely correct.

This actually makes sense. Due to how diminishing returns works, the more Dex you stack, the less effective dodge you get (as noted, you show in the gradation that you get very little dodge as you add more in -- after 1k Dex, it takes 1k to increase dodge by 10%).

It has nothing to do with diminishing returns. DEX is universally bad, even when it's at the start of it's curve, it's worse (for defense) than any other stat, and just gets worse from there.

Because the only two classes that are going to be looking at using Dex are the Monk (HtH) and DH (ranged). Dex is not something that really a Barbarian nor a WD or Wizard are going to be looking to get because it doesn't affect them. Because the two main classes that use Dex, one's ultimate goal is to keep out of melee combat (look to Evasive Fire and Vault on the DH) and the other has skills based around improving dodge (Mantra of Evasion along with the Passive The Guardian's Path while dual wielding) and can use Dex in the place of Str for Armor (Passive Seize the Initiative). As such, it makes sense that Dex doesn't add too much to your dodge chance. A Monk running with Mantra of Evasion and The Guardian's Path in one of the Passive slots and dual wielding has 30% base dodge before even looking at Dex. This means a Monk with 1000 Dex has 60% dodge with the above two skill active. So, there's definitely a reason.

I also don't understand why you're talking about other games as if there is some kind of universal law of gaming physics that health is always the best defensive stat. That's not the case in some games (Skyrim, for example) and brings nothing relevant to the discussion of stat priority for this game. In this game every defensive stat other than DEX does the same thing health does because it universally reduces incoming damage. Not some of one type and none of another as with most games, where armor reduces physical damage and resist doesn't.

Getting off topic for just a second, last time I checked, Many/Most does not equal All. There are a large number of games out there that follow this same kind of mantra that Diablo 3 is running where overall Health is more likely to save you than any other defensive skills.