I tried to make a mission once, that involved a disabled Diomedes, and eventually, a Karuna jumping in on top of it. . .
I couldn't balance it - even with the armor at HA20, the Diomedes would take out the Karuna before the Karuna had managed to take more than a couple of % off of the (LA100) Diomedes. This was after over a squadron of bombers had spent the mission targeting those beam cannons.
Anything that is remotely over the Diomedes will get shredded in short order. The Karuna will peck things to death slowly when it's about 2km further away, which isn't as much of an advantage as you'd think.
If you've ever played The Darkest Hour very often, you know how often the Valarie ends up killing the Wargods before they ever exist.