Hi ! I play skirmishes with Legion and I noticed the Xyston T2 air defence is barely doing any damage (sometimes 1hp, most of the time 0).
Actually, I find all Legion air defence quite undewhelming (T2 minigun, planes, etc) but at least it has SOME effect, so I guess it's a balance choice.
If that can help, here are my game options :
EMP Rework
Energy Share Rework
Air Rework
Release Candidate Units
Extra Unit Pack
Legion Faction
Game Ends Mode : builders