Strategy:The Mortuary

Don't attempt storming it unless you have serious firepower and nuclear plasma rifle (or some other infinite-ammo weapon).

If you have Napalm launcher, you will have MUCH easier time hear, because each shot effectively kills all enemies at blast radius, leaving no corpses and creating area impassable to viles and most enemies.

Entering level with Berserk, Invincibility and/or goggless help a lot. Health level matter less, because there are super-health globes near entrance.

If you don't feel prepared good enough, but have homing phase device, and is not aiming for YAAM, it can be worth visiting just to grab some goodies (modules, Nuclear BFG, Assault Shotgun) and leave expeditiously.

Basically, there are two parts of the fight.

First, kill as much Viles as soon as possible, while moving to Nuclear BFG9000 in top right corner.

If you are lucky, you will kill ALL of viles this way, saving you a lot of trouble and resources.

Otherwise, you will be at one side of the room, with a horde of risen dead advancing you from another. So, start killing them from maximum distance, giving preference to infinite-ammo weapons, and firing with nuclear bfg or other explosive weapon to clean up corpses. You can see corpses even out of you range, so you can see when they disappear - it means they are rised and vile is somewhere around. If you play above HNTR, it can be good idea to demolish central structure, so enemy will not use it for suprising you. Also, if you don't take/destroy read armor, enemies will take it instead.

It is not impossible (and very badass) to clear out mortuary with melee, especially as Vampire. You will need good dodge rate and speed, so at least HR2 is a must. Also, any non-indestructible armor you where will most likely be shredded very fast. IT is much more problematic on HMP and above, because of Commandos.

Slightly less badass option is to hole up in corner or central structure and kill breakaway monsters one by one. Works both with melee and ranged. Corner rooms have worse cover, but in the central room you can be attacked from more sides.