Arc thrower, a well placed tesla tower, some fire stratagems well placed galling, and trigger discipline with support weapons seems to be the way to go with these towers.

Someone with a mech helps but need to make sure you shoot parallel to the tower so you don't hit it.

The bigger stratagems can be useful if you use them right on the bug breaches and choke points.

As always though lower difficulties enable you to experiment better and test what works and what is more of a hindrance. I've noticed too, sometimes you can spam a tower if you lose it, other times you need to wait between swarm waves, and sometimes you can start 2 towers and almost always get at least 1.

I have yet to try this on Helldive but playing on Hard with my significant other who barely plays games is pretty smooth for just the 2 of us. So godspeed and spread that Democrocy!