Kayn's abilites only scale on bonus AD, so playing him tank or such isn't really an option. Doesn't this make him an AD Mage?
He's an AD Battlemage.
Because the point of battlemages are mages who can stay in combat but need time to kill the targets, yet also have moves to completely evade death.
That perfectly describes Kayn. He can come in, evade death and kill someone as long as he has a little time.