I'm reminded of his line of "I may be no warrior but I've learned to hold my own over the years." When he went into the tower he was primarily an archer, I'm sure he had an understanding of some other fighting styles, but that was how he defended himself. By the time you encounter him again as the Exarch, he's an old man and he's been through a lot, from his stories and dialogue the one thing he's been trying to do all this time is fit in, play what ever role that was needed of him. I know he was an omni-trust there for gameplay but I like how it fits the man he became, he's learned many tricks over the years and had likely had to fight in all manner of ways so he's flexible, with the tower backing him up he could pull off many a manner of abilities others couldn't, while he's lost the tower, he still recalls all that, so he can still fight in different styles. I'm not sure if they'll develop that any more, the scions are their own breed when it comes to their jobs, some more than others like with Alph and his endless Carby's or Y'shtola deciding she wants all the schools of magic. He is using his younger body, one that until now wasn't casting spells, he points out just how exhausting he finds doing magic, perhaps once he's more used to it he'll start using other spells or forms, who knows.