I've played as Austria (until I got an error and had to start again) as well as Prussia. I'll admit that I haven't played more than 1.5yrs of game time. But, it usually doesn't matter because as Austria Prussia doesnt join, and as Prussia, the French roll over Wien which is always undefended.
But my main point is, that Russia never does anything except send some lone artillery west, and the UK never lands troops anywhere. Make the game very difficult to survive or enjoy as coalition. Or, is it me?