It is because many players complained that they or the NPC would get too easily CC spammed after their magic armour was down making the game too easy.
That change does not really tackle the difficulty issue since the NPC will also need to CC you twice.
Maybe if all soft CC like slow (chilled and shocked now) would still affect the NPC if he still has armor on keeping some kind of CC effect. Might not be great but I just would like to see it.
Now for the casters damage, I had no problem with it.
I have to say I like the crit builds and I've had crit for 500+ with chain lightning, it's fun!
