That level is not too bad because of the long corridors in the middle and the side room. And when they reach you in the side room you can just climb up, jump back down and start sniping them from afar again.I think I might try luring the Revenants to the rooftops. (Yes, they climb ladders — I found this out the hard way)
If I can separate the Revenants from the Napads, it should make that level a bit more... doable.
Anyway, is there any point to using SMGs or pistols unless you don't have access to any other expert skill? Assault rifles seem to be more damage per shot always with a similar or higher ammo pool, and imo there's no reason to not take a shotgun+sniper+magnum if you have all slots open.