This ability is not even close to OP, but one of its biggest weaknesses is not very well advertised. I think a lot of players see AT overwatch demolish an isolated tank and conclude that that's what the ability does to the whole circle, rather than having a pretty strict cap on the number of projectiles it has and distributing them across targets.
^This
Its no crazier than Sector Assault. Sure u can shoot those planes down but usually they get really good dmg in before u can