Firstly love the good discussion going on here. I think your last point about crit adjustment is the exact reason i enjoy having them seperate. If we remove the other aspects we could gear for crit, then its only a matter of time when crit does get adjusted, because we will have almost no crit stat to stack besides Crit chance.
In my opinion its self fulfilling with such a change. If you make crit into a single stat, to make crit feel like its doing anything at a certain point (lets say lvl 50 with full AF) then when you start getting better gear, or multi melding, your crit will be high, which in turn means that an adjustment is coming when either new gear comes, level cap rises etc.
Thats in part why i support the current crit stats since they assist in keeping the overall damage in check, and would in general, require much more minor adjustments if needed.
As to using evasion as an exploit. I can understand stacking X means an evasion heavy class can do alot of broken things. Though i'm not familiar with your first example, i am familar with the second. I think its much better for us to instead of looking at it as its been used badly before, get rid of it to how could that be avoided in the future?
For instance if we discuss the merits of Evasion being a "gear only stat" and reciving no benifits from classes? Thus any evasion numbers would be kept within a certain range. Apply acc vs evasion modifiers for boss vs player? Maybe some extra ACC depending on distance from a boss during attack? (Higher chance of evasion when 4 yalms from boss then 2?) In essense engineering evasion to be something that works better during escape of an attack range, then a "stand there and dodge it" stat?
To me this type of discussion could be more fruitful to all involved then just Evasion or no evasion because we discuss how we as a playerbase would like to see Evasion work. Yes/no discussions rarely spark any ideas. We should look at the examples you provided and try to find the mechanic that can then make such an exploit/use less, Useful?