that picture doesnt really explain why he's an idiot.. if the champion is that good at lvl 10 and can beat the crap out of enemies, then maybe he can take on all those units by himself..? Or if this is not the case, should he have immediately fled the battle or not have entered it to start with?
He could have cast some powerful magical spells and blew them away.
It's getting the AI to cast magic spells intelligently that will have to be looked at.
The spell system in FE is totally different than WOM but it has a lot of AI tags available to it which lets the AI potentially do smart stuff.
And yes, technically, he would have won this battle if Relias weren't there too because he does all Matrix-like on archers while taking companies down in a single swing.