Well, I'm still not sure on the rule regarding custom classes. But here's what the Barbarian class would play like.

The Barbarian, powerful, quick, and self healing. This class is a double edged sword, for every HP lost they gain a damage bonus. And siphon health according to that damage multiplier. However friendly healing is considered a form of attack, and thus only inflicts HP loss on the Barbarian. If a Barbarian is not killing enough enemies to restore their health fast enough, he may only use potions to restore HP. Thus an effective Barbarian is always on the edge of death in the midst of battle.