despite the ridiculous overpowerdness of the illums themselves. I dont think they are the main problem with balance. The problem is every counter to the illums can be simply blocked with a ship or a technology. THe counter triangle is
Illum-->Lf--->Carrier--->Illum
but then flack comes in and breaks the triangle makeing it.
Illum--->LF--> Carrier. <---Illum
the early game counter is gone. with flack illums then counter all early game units except scouts which can be countered in countless ways.(mainly with repulse)
The next problem is late game with repulse, illums counter everything because even HCs cant reach the illums.
making illums OP because they counter all of the units which were designed to destroy them.
Advent is is the only race which can effectively break the counter triangle making illums more powerful than every ship becasue they counter absolutly everything with a couple of ships and techs.