Casters are not being nerfed. The 11% cold/6% other element crit chance nerf is about 5-10% dps loss yes, but the master of X feats are 10-20+% dps buff depending on build, and the caster level buff is roughly a 10% buff on top of that (again depending on build). Perhaps there are some obscure builds that might end up behind from theses changes, but the vast majority are coming out ahead significantly.
It depends on the build - my dark bargainer warlock made out much better than my fire sorc.
Warlock
-6% crit chance (I knew this was never intended to stack so I consider it a fix)
+2 blast dice from change to epic pact dice feat
+3 pact dice from swapping redundant crit chance augment with pact dice augment I couldn't fit in
+ proc damage from master of force (although I don't think it can possibly be a 20% dps buff as you state). There is no feat tax as the epic eld blast feat is now auto-granted freeing up a feat spot for this.
With my exact build the dice and crit chance net to an increase of 2.67% damage so pretty neutral. If I add in the proc damage it's a total increase of 14.4% damage from Normal through R6 in line with your estimate. In R10 it's an increase of 48.7% damage so it's a massive buff in R10s which was needed. Also not everyone runs R10 and many of those that do don't exclusively run R10. So it's a big increase, but not necessarily a game changer for everyone.
On the other hand my fire sorc gets less than a 10% increase in single target damage total even with master of fire which I will have to fit in. I don't take intensify currently because I found with it my spell point usage was too high with. So if I don't change it I lose 50 spellpower on top of the 6% crit chance. The main strength of the build is clearing mobs in quests solo and with the change in meteor swarm this is a little bit less effective. I will probably reroll this character to something else, although I wouldn't exactly call it weak - just less effective.