What can I say, use cover and have your team take enemies down. don't expose yourself unnecessarily because you will get killed. The hardest is going to be storming the building at the end to lase the nukes. Just use the tank to cover you and have your team clear out the enemies. Only pop out of cover to take down one or two enemies, any longer than that and you will get shot. Use smoke to your advantage, that's why they gave it to you. It took me a couple of replays, and it is frustration because there is no save point once you start storming the building so if you die while you are lasing the nukes you will have to start all over again from the bottom of the building.