I managed to find a few spots;
*Once you respawn you can enter the disco area then follow "Stairs" sign to climb the platform on top of disco &bar where zeds will come from 2-3 different locations and a trader. Biggest issue is Sirens, not the big targets, 2 Commandos or Firebug and Commando, one at each side needed. Please no Bile Thrower medics, that's retarded.
*If you follow the gate near trader and follow the stairs down, there's a second floor trader, where you can peek your head out to see a long hallway where sharps can easily defend with the help of focus fire. the stairs at the behind can be hold by 1-2 people, preferably a Support Specialist and a Firebad or Commando for shushing Sirens.
*When you head ahead and down, go for the most below trader which is at 4th floor, there's an even better spot. Just use the right side door from the metal stairs instead of the front and you'll find yourself in the large surgery room. Trick is, there's a crawler spawn in the middle of room, one Commando or Support Specialist should stand by the locked door to hunt them down.
*I now tend to stay away from the 3rd floor, can't figure out a good hold there yet, and I generally get lost in its hallways.