I also started both characters as warriors, and kept them that was for most of act 1, since skeletons are vulnerable to crushing damage (DK used a sword, the hero used a club or fighting stick). My hero was also a part time archer, which switched to mostly full time near the end of act 1 (upon reaching the citadel).
The really effective spells (shaman magic) are available starting in the second act, so waiting to build a mage is not going to hurt anything, either.