Hmm I'll have to take a look at the code and see if anything stands out. Not sure why it would cause slowdown that drastically other than a lot of the effects being on screen. Out of curiosity, did you encounter slowdown when you deployed a bunch of wings that phase in and out - like the spectre?
It could be something unique to how the system's glow works though. I'll see what I can find out about it.
Currently my fighter force consists of majority Banshees and Broadswords, I may have 1 spectre in there somewhere. Even in something like the simulator the moment i activate the ability with the malevolence class, there is a definite performance hit, and the game does slow down. i can have fairly large battle with little to no slowdown, but as soon as that ability goes off, it tanks pretty hard for as long as it's active.