So, while I completely agree that the respawning rate needs to be slowed down (I don’t mind that it’s infinite, kinda makes sense), you don’t have to completely cheese your way through a lair to win.
TL;DR The enemy can be shepherded where needed, a lone soldier can kill the spawnery
I got a little tired of them (slogging through the “conventional” was doesn’t work, you can’t make progress with infinite enemies, by grinding them out) so I set up a designated lair-strike-team. [Admittedly, I’m fairly far through the campaign and have allied with all 3 faction] but my team consists of 3 jump troops, a sniper, an engineer and an infiltrator.
The theory has worked a number of times now, with little effort.
Run the infiltrator out one direction (well, it’s usually through the centre first, till you find out the path), I run mine with a gauss machine gun, for the needed extra damage. [An assault rifle should suffice, dual classing them into assault is a great idea anyway]
I then jump my team of 3 heavies in another direction, off to one side (often the side I DON’T think the spawnery is on!) away from the infiltrator. Set them up where necessary and/or keep jumping when you can.
And finally, I have my sniper and turrets. They stay around the entrance, and make as much noise as possible (shoot everything!)
So, the idea is this. The enemy will be drawn to one or both of my visible groups. Any I kill will respawn and do the same. 90% of the time, my infiltrator gets an easy path though to the spawnery. In the other times, my jump team makes it there and deals with it instead. The reason I use 3, is you can often lose 1 or even 2 (to a siren, or too wounded and needs to hide+heal) and still kill the spawnery. Each is capable of doing it alone.
Finally, (added to all my other ramblings). I have 3 factions to draw from. From the Anu, I have a priest with the willpower aura and a heavy suit. They jump along side the other 2 and all of the willpower needed for jumping is “freeeee”. Which means, you never have to stop