Having him as a team player isn't really necessary; his magic makes him a powerful member to a party regardless. Better for him to deal out damage on his own, anyways; it's comparable to most dual techs and more attacks can be done in the same amount of time when he can't team up with another.

He was a great chracter. Everyone thought him an evil bastard, but the Monsters were the only ones who had his back, so when he took control, he took their cause. If he ended up in Guardia, it might have been different.

As for him dying in the end, that merely depends on your actions. Glenn's human? So what? I also see Magus flying around searching for Schala. Different endings.