Combat Skill - the number of points affects how many attacks you are allowed to make against a particular enemy in one turn.
Defense Skill - affects how many times you are allowed to dodge or block an attack.
Killer Skill - affects the number of enemies you are allowed to kill in one turn.
Magic Skill - affects the number of spells you are allowed to cast in one turn.
The health mechanic doesn't work here, in my opinion. Heroes with 20 HP can walk around and fight without paying attention to serious wounds. It would be much better if injuries were received regardless of how much HP was lost. If your leg is injured, it means it's harder for you to walk, regardless of how much health you have. If you are injured in the arm, then act like you are injured in the arm, and don't just brush it off with a cheap (-15 HP) penalty. That's stupid, in my opinion.
And the spells that players have, regardless of their power, are learned as the game progresses. At the very beginning, mages are allowed to have a maximum of three spells.