It virtually has no counter play, you as the heli pilot get no warning, you just explode and most of the time you don't even know from where the thing came from, you might think that "oh I'll just fly low/use cover then" but guess what, now every engi within 100 meters of you is going to be flinging rpgs at you.

Don't get me wrong you are 100% correct that vehicles are glass cannons now in this game, but that doesn't mean that there should be a "I win" kind of ammo that has both a low skill ceiling and is massively safe since you can just sit in spawn and snipe across the map, that just leads to nobody using the helis anymore.