I actually tend to forget I have a lot of power ups to use. Are power ups actually going to make a difference on this difficulty or would my Level's be put to better use by getting vehicles? I understand that Damage Boost and Overshield may help, but I certainly cannot see Active Camouflage or Speed Boost helping in the slightest.
9 times out of 10 you’re probably better off with a vehicle than a power up though with that being said I do find an overshield handy every so often if I’m trapped in a building defend round without a vehicle. Since OS recharges your shield & gives the additional protection too they can be pretty good.
As for Camo, speed & damage boosts...I’ve never found a significant use for them in my time playing Firefight.
Maybe a endgame laser with a damage boost if you can stay alive and save the REQS. Can be good against the grunt mech shield, other than that I found no use haha