It seems they are convinced that the Deathknight will be better suited as a mage in the long run.
Yeah, but now you're just talking about power gaming vs roleplaying. If you want to play the DK as a mage just because it makes the game a little easier, you might as well play Diablo 2 or another action game. To me, I just can't see the DK as a mage (or as a survivor for that matter), and I just got done a successful stint as a pyromancer in WBCII (of all games), so I wanted to play a fire mage in this one. I will roleplay these characters, in spite of the fact that I am not taking the easiest path through the game.