Fighting undead

[asprah]

Ok I am a still a bit newbie so I apologize if this was answered before- I coudn´t find it.
My question is this: what is the most effective ways of fighting undead without taking losses? I know UD are weak versus holy dmg but I really do not have any holy dmg spells besides heal in my spell book.
I am warr lvl 7, got 2 spirits of rage active atm, got lvl 1 order and distortion skill and the rest is invested in might skills of course. Units I am using mostly are guardians, ancient bears, archmages, priests and bowmen (snakes are out ).
My point is that I almost have no losses in any other fights but I just can not fight the undead without losing some- am I doing something wrong?

My other question is about incorporating undead in my army. Does it worth to take Dark commander skill since I would like my army to consist of undead mostly at some point? Or is it worth to mix armies no matter of moral loss? I would really like to know this before I invest points in that skill because I would not want to start all over again just because I screwed up with my choice of skills.
Ty!