Not all specs can do same things equally well. Some are good at burst, some at multidot, some at cleave, some at execution, some at AoE, etc. Be happy that there actually are talents that can help you with upping the part where you are lacking.And like you said yourself: Multi-shot is only a small part of AoE damage for Surv and BM, but MM would benefit a lot from it, and MM is already far far behind the other specs in AoE damage (and guess which spec I play?).
I don't pvp a lot but something tells me the amount of times multishot is being used is very little. Apart from that there's perhaps challenge modes, and even those can be completed with supobtimal talents/specs.And BTW, you limit your thinking to raids only. I'm not a great raider (I'm above the average player, but far behind serious raiders), but I do a lot of things in this game, including PvP. I don't care if there's 1 fight or 10 fights in which AoE will be important, I care for the fact that AoE is not buffed at all.
When I make a request, I'm not constraining it behind one aspect of the game, but how it will impact the game overall. When I'm out in the wild without a pet and pull several mobs, I'd like to be able to kill them a little quickier since I don't have a pet to tank them.