But then, perhaps it ultimately goes to level 20; I don't know. A lot of useful information is missing from the manual, in my opinion.
You can train to level 10 in any skill, assuming you find the right teacher. Just think of the mana requirements of a level 10 fire missile, though, even if you don't add other elements to it.
I'm playing the same combo as you. I've only just finished Act 1, so I'm hoping there are more teachers of mage skills relatively soon. I want to specialize in fire spells, but so far I have to be content with training my mage to be an archer and using fire arrows to be effective in combat. I've heard the DK can have problems in the later Acts with combat, but I'm hoping that a strategy of focusing on alternate skills like poison, evade and armor use and pumping up my critical hit chance will see me through (unlike the mage, my DK has not had a problem finding useful skills). Also stats like survival and speed in addition to strenght, agility, and con are very useful.
Another thing I've noticed is that it seems like (especially for the combat skills) you put a point in something you get a big benefit, but further points result in lower benefits. Almost seems like the devs want you to spread out your skill points to multiple skills to be most successful, at least from my perspective.
