I agrea with vivalafai on some points, that the actual system has good points and i like it. Trying refont him like you can be stunned proportionnaly to your armor is quinda killing it. better leaving the armor totally in that case.

I would sugest a simple think that will make mages (because they are really weak as dps, they can only be good support , sad tought) a bit "in the game". simply putting to cc spell damages bonus proportianal too the cc they are applying (in the case the target as again magical amor).

An example is alway better: i cast shoking touch (that deal 20 eletric damages and stun) on a zombie witch with 40 magic armor, it break 20 magic armor and can stun, so the stun (that isn't stunning tho) deal additional 5 (maybe 8) eletric damages. This would make two birds one stone:
~giving mages a little up (not making them op tho)
~making you less recluant when using cc spells on a ennemie with hight magical armor (and so said making thoses spell a bit better maybe).

Same goes for the burning, and buffs effect damages i guess?

PS: this is far away from buffing the mages to the point of "overpower". i mean i killed the voidwoken the a lvl 5 team because i had one ranged with the new polymorf, and in thoses 4 lvl 5 characters i had 2 thats din't played a single turn (one glass canon of a friends was usless and the other loshe when full beugged and couldn't use spell). Sorry saying this here but ranger with polymorf is kinda unfair to the game lol. (killing 3 ennemies in one turn is kinda rude :p )