I've done all of the T4 bosses and a few in ZA, and the only boss that really gives me trouble in any of the raids I've done is Illhoof. However, I've usually been fine since the two other healers in the group were tremendously overgeared. Of course, that means that now that my guild is having overgeared people sit out so undergeared people can go in and roll on stuff, instead of just DE'ing stuff, I need to get my act together.
My main issue is switching to the chains when someone is getting sacrificed. Regrowth isn't the quickest button I push, since I have lifebloom and rejuvination a lot more accessible. Is there a way to know ahead of time who he will target, or any suggestions you can give me to target heals on the chained person? (i.e. a macro or anything).