Like some have said already - on Vader, ATC is auto-include and on generics accuracy corrector is better.
As for whether or not ATC is overpowered:
- It requires you to spend an action first.
- It requires you to keep that TL'd ship in arc
- the TIE Advanced was severely underpowered
So yes, in a vacuum, being able to add a crit for 1 point might seem broken; but the TIE Advanced was broken in the bad way to begin with. So this is really just a patch.
Accuracy Correctors might seem overpowered on 2-attack ships, but again - those ships were severely underpowered to begin with. This is FFG's way of saying "Whoops, we should have given these guys 2.5-3 attacks."
Even if you ran the maximum 4 x ACs, you're really only dishing out the damage of 4-5 TIE Fighters. If your opponent is whining about that, tell him/her to fly something with more than 0-1 agility.