I've said it many times, but I'll say it again. The balancing of a ship depends on the environment it is placed in. Sure, one Erinyes is unbalanced when pitted against a lone Loki. But is it a fair comparison? Pit that same Erinyes against two, three, even four Lokis, and things are getting stacked in the other way. Or have it opposite an Ares, which would possibly be better matched.
An excellent example of this is the Colossus. It is armed with several LRBGreens - these things will pulverise any destroyer class without even breaking a sweat, so you could argue that they are unbalanced. But against the Sathanas, the mighty LRBGreens are in fact very weak (when compared to the BFReds).
Make note of this: for uber-ships like the Chimera (both of them, if the Shivan one becomes like the one in the
Machina Terra campaign), maybe you could consider putting them in missions a different way. Instead of having four of them to a wing, make them fly in pairs. There you go, balance.