An Engy shouldn't have to deal with classes. Just throw EMPs and run. And you should always have the wrench, or a double-barreled shotgun if there's lots of enemies. Off to the left of the main entrance, by the water entrance. Softens people up before they enter.
Enemies can bounce grens off wall and easily kill it.
At the split, the corner of the room on the right, facing the elevator. Tears People up quickly. At the top of the ramps. Most people come through there. Nobody puts one here, ever.