Andras certainly isn't stupid. Not only is he a skilled tactician and fighter, and a powerhouse (though Jezera is just as lethal and brutal when she wants to be, ask the elves), but he has the loyalty of the orcs you've been recruiting. On top of that, even if you have a very virtuous playthrough as Alexia, she's still tempted and curious even though she knows he's a Bad Idea (tm). See also Ironhide, who she can befriend with a minimum of sexual tension if you decide to make those choices.
So he's smart enough to command an army, tempt Alexia even after he stops playing nice, and he's got the same body sprite as Rowan. He's basically his evil twin.
That said, I kind of mentally play the game from Alexia's perspective because there's more joy there. Everyone has their own thing, but Rowan is one gloomy dude for someone who is getting laid so much.