I had a chance to play engineer for 4 hours on one of the last stress tests. It seems like with their second healing ability swap, the med kit, they could be the closest thing to a true healer. It was worthless on the story arc mission because the NPCs would not use them. It would be really enjoyable to use with other players. I could not level fast enough to unlock flamethrower > <. I could see really enjoying this class.