In my experience the balance in non-ME Random Battles with all-default settings (100 %/XXX) is pretty much off.
Attacking/Advancing, my usual result against the AI is a decisive victory. Delaying/Defending, I am glad to get a draw. I am normally much better at defending, so that says something.
I am quite positively certain that holds true between human players: Default Random Battles, attacker will win much more often than 50/50.
I find the game otherwise very realistic; this actually supports my argument that the balance is off, because irl, if given 3:1/2:1 odds, the Assaulting/Advancing side should win most of the time. For 50/50, 2:1/3:2 would seem a better match.
I mean, really, would any human player want to be the delaying/defending side in a random default game? I rest my case.