I agree that a sniper using an Accurate weapon can take out an NPC in the first round of combat - but, they're a sniper. That's sort of their job. It's a bit like saying that the flamer-wielding priest can hold back the insane cultists. Accurate's aim bonus isn't massively overpowered, and the bonus damage only working with single-shot means that it rewards sniper rifle/long las users.
The argument that this will give more use for bipods/tripods... well, yes it will, but why is that a good thing? We could insist all snipers must have a spotter using a handheld targeter - that would increase the uptake of that item, because what party has a mortar to hand?
'Nother issue, of course, is that while a sniper with a high BS and a red-dot long las making a Standard Attack can reach 90-100, that's before any penalties are brought into effect - smoke, haze, wind for SP weapons, any protective gear the NPC might be carrying - it's swerving a little into metagaming, but if you as the GM have a single valuable NPC that the party want to kill and they have an ace sniper, maybe you should kit the NPC out with some kind of force field or something. Or give him a boost to Dodge. It is only a single shot, after all.
The other problem with this is that it will eliminate the possibility of sniping taking one turn. And that is a problem, because even the best sniper is only killing one target per turn. Which, if you've only got one NPC on the enemy side, is an issue. But if there's two dozen axe-wielding cultists charging round a corner, making the sniper take one shot every two turns is going to render him worthless, especially when he has to take a talent or suffer penalties for firing into melee.
TL:DR: Accurate isn't that bad.