I'll update as I do more of these.

General:
Scaling gets wierd if you upgrade the turrets to much. You can make these much easier by simply upgrading the center and only upgrading one turret when the boss spawns. Upgrading any turrets before spawns an insane amount of super powerful invasions. So the scaling probably needs to be tuned a bit. Make it so that its less of a drastic curve. It seemed that not upgrading any made it far to easy to complete the first stage.

Ludvanor:

This Planarch is alot of fun. His shield mechanic stumped us a bit at first. It appeared that you had to fully upgrade the turret for it to penetrate his shield. Not sure if this was a bug. His Pus spore AOE didn't seem to pose much of a threat. We never really got close to dying and were basicallly ignoring the mechanics. His frontal cone attack Should do a little more damage for sure. I reccomend adding a damage return component to his shield, at least make people stop DPS or risk wiping themselves. I'd also make it so the AOE dot poison will do more damage the longer you stand in it. Something that forces people to move. Four people shouldn't be able to overpower the mechanics for this guy completely. Unless these are designed for 3 people or something.

Overall though it was alot of fun. The chest loot was pretty awful. Should at least give decent greens, if not a blue.