There is no right or wrong. You seem to have already decided which stats are going to be in the game, but you haven't figured out how they should work yet. Seems kind of backwards if you ask me. Look at this article: http://psychochild.org/?p=377
. It analyzes WoW's attribute system, and you seem to have similar "problems" (magic only being affected by one stat for example). Also remember that WoW factors in the level differences between players and mobs. Higher level mobs and players are almost impossible to hit for much lower level players.
EDIT: And the WoW attack table: http://www.wowwiki.com/Attack_Table
. I'm not saying that it's good, just that it works.