Now, I knew the 4pc change was going to push us to T15, so I jumped on early to the change and got re used to a 6 sec CD on HS. As far as mastery goes, I'm back at the pre nerf level between item upgrades and dropping spirit to roughly 11k. I had 15k spirit. I was ending fights at 50% mana. I now end fights at sub 25%.
In all honesty, it's not as bad as everyone seems to make it out to be. You just have to adjust your style. (Note: I do 25s, so I'm not speaking for 10 mans and have no idea how this has affected them. I'm assuming that most of the negative feedback is from 10 mans, since it is the majority of raiding in the community these days.)