I'd say he is useful as a singer, definitely, the buffs when he sings for an unit makes him better than the original Azura, Ninian or the original Olivia. As a battle unit, he's good for himself and others Blue Tome users only because of his B Tome Valor skill which at max doubles the SP he gets. So at an Arena battle where he is a bonus char, he would get 24 SP for each enemy he kills... but that gets old quick, as his skills doesn't require that much SP. Black Knight is much more time consuming to max than him. Anyway, to sum it up: he is an average fighter, but great support (especially if he's supporting another Blue Tome user.