I say yes and no here.
You proved the enforcer is weak, but the enforcer has reintegration. Perhaps the fix here is to lower the time it takes for the Enforcer to heal itself (From 720 health over 40 sec to say 720 health over 10). It's tough to balance the enfrocer because it's the only HC with a healing ability. The devs did that intentionally. The skirmisher and enforcer are each a little weaker in the grand scheme of things because they get to heal mid battle.
I will say the skirmisher needs a buff in DPS. Why does this ship do 10 dps, as much as a cobalt? 5 ship slots vs. 7. Skirm should do 12, not 10. If no reintegraiton then 14, but since there is reintegraiton, 12.
Assailants and LRMS fight each other off well enough. The illum needs a nerf, but how drastic, I don't know. LRMS and Assailants fight differently than Illums. Illums are meant to destroy fleets and because they're tier 3 they bring a more drastic effect to rush maps , i.e. the online community, than its counterparts. Illums are the only ship I would say is designed to destroy enemy fleets, so I'd say that's where the IMBA is coming from. Oh, and instant hit. Have I mentioned the instant hit? Oh, and the incredibably high health that makes them tougher than HC's in the grand scheme. Have I mentioned that too? Hopefully a fix is a'comin.