ok, i was wrong about the trinity, i'm sorry for what i said.
As for the Sathanas, if its supported by a few Ravanas and Demons, it can put up quite a fight as the destroyers can protect her flanks either by waiting at her back or by engaging whatever comes at the Sathanas from the sides before they reach strike range.
The best use i can see for the Sathanas however is the same role as modern day heavy artillery; it can hang back and provide heavy support for fighters/bombers, cruisers, corvettes and of course destroyers. They may not be suited to the kind of close range fighting you see in the GTVA's prefered arena, but the shivans would likely -create- their own conditions for waging war dont you think?