melee classes and hunters should, as a rule, be hit capped during raids of their own accord (tanks excepted). for raid bosses, this is around 9% to hit. combat rogues often stack more hit than this, but generally anything past about 10-12% +hit is considered overkill for dual wielding DPS wars and rogues. hunters, 2h wars and ret pallies should be at the hit cap with their own gear without even really trying, while enhancement shaman get a lot of +hit from talents. added to what they get from gear, they should be pushing 12-13% without too much trouble.
so, in other words, with the exception of combat rogues and some of the tanks, you wont see much of a gain with imp faerie fire. in a dps build, its makes much more sense to stick those points elsewhere, as they wont benefit hunters, 2h wars or ret pallies, are of marginal gain for fury wars and enh shammies, and are only really useful for combat rogues (who have plenty of hit without really trying).
as for the talent point sacrifice, youre basically giving up max intensity and 2/5 points in subtlety, assuming you went with a balance/resto raid build. thats a lot of -threat and regen out the window.