Ops are quite useful all the time. I agree that they should be able to dehack an objective, but you're simply looking at objectives. Yes, the game is all about objectives, but when I do an objective for any class, I can't do it without teammates... If an operative is keeping an eye out while I am doing something, marking enemies, marking mines if I am about to plant a bomb, com hacking (which I am amazed so many of you ignored, perhaps no one pays any attention to the map that tells you where the enemy teams is... one of the most useful things you can ever know and probably the most important role of an operative), I feel much safer. When it comes to defense they don't play the largest role, that is a fair statement, but it's not an issue of class balance. Some games simply can't be won without operatives. Stacking 8 turrets on each other? EMP and op takes control of all 8 of them... Ops are easily one of the most useful classes on an attacking team provided you don't have a team with 8 of them lol. And when it comes to defense they still have caltrops (more useful than you would think), the ability to take control of allied turrets to allow them to focus on the objective (because sometimes they would rather shoot the guy in the corner than shoot the guy that's planting the bomb!!!!!!), and they can also tell you where the entire enemy team is (once again, most useful thing ever IMO, nothing makes me feel safer than knowing where bad guys with guns are). If they gave ops de-hacking I think it would be perfect, but as is, they are pretty amazing anyways...
Engineers don't really need nerfing either I don't think... Sure they can buff guns, but so what? It's not like you need 8 of them to do that. And sure they can plant mines and turrets, all the better for the op to take control of. The beauty of Brink is that everything has a counter. No one class can become invincible if you have a team that is smart enough to tactically approach every situation, diffuse it, and accomplish the objective. It's not an issue of class balance, it's an issue of human intellect.