Smoke Grenades in DC are useless, as it's a complete Rambo mod. If you try to use a smoke grenade as cover, the nametag will give you away. If nametags are off, people will simply walk through a pillar of smoke. They'll either toss 'nades into it or shoot into it to make sure noone is in there, then they won't enter it in case it is rigged to blow. Marking targets with smoke doesn't really work because most pilots either - A. Aren't playing as a part of the team. B. Can't hit the broad side of a barn. Smoke is pretty much useless and annoying, because Pilots won't bomb it and the only way it can effectively be used is to coat a sensitive area in smoke, which pisses off the other team tremendously.
If enough are used in tandem, it could obscure movement of a tank or two, like destroyers around a battleship, 'course the tank could always waste whatever it is being hidden from.