Isn't molten core shot from the claw? I wouldn't give it for granted that he'd be able to strike him precisely, since he'd be hanging down (not even necessarily hugged), and he'd have to shoot behind him without proper aim while going at high speed, and this assuming he can do it before Vulture decides to just drop or launch him away. Vulture also has a record of slamming people onto walls and such, so Torb might not even been carried for that long, before Toomse decides to attack.
That is surely something indeed, but it also extremely situational as a feat. He was fighting the omnics in groups with allies and his general role doesn't necessarily mean he was in the frontlines, even when operating in a small platoon. This to say he can surely handle himself, never denied it, but so far he lacks some feats in regard to 1v1 combat against such an opponent.