I'm the reason a particular druid removed innervate from whisper cast! LOL!

Hunters on Onyxia == awesome for innervate ;)

Other then that? You have to look at effective healing? It depends on who gains the most from the heal. Paladins could arguably be named the best class to use it on as their efficiency is pretty much the highest of any class, but it boils down to who's the best player really. If you're a shitty healer, and run OOM quickly when having a poor healing effiency then you're not a good target for innervate!