I don't see any real reason to not pre-buff in 8 man content unless you are ridiculously overgeared for it. If you're doing Ramuh EX, that's not going to be the case, so, uh, pre-buff?

On the other side of it, I don't understand why people demand pre-buffs in dungeons all the time. Just, like, keep it going. The time spent pre-buffing is time we could spend fighting the boss and getting out of the dungeon faster, yeah? I'd pre-buff if they are about to pull an entire wing of a dungeon, but that's about it.