Probably, for a tactician, if you're moving around with an army and a Necromancer, it's better to level up Combat (it's some kind of help in battle). If you don't have anyone else besides him, then it's probably better to level up Magic (Death). But if you have a Necromancer and you don't want a tactician or a melee fighter, then level up some other magic (it's up to your imagination and what you feel like). In general, in such matters, only desire works, one way or another!!!!
P.S. (I also practically don't play as Death... I don't like it, but I adore magic)