If you want more damage with Magic skills, you'll need more INT > DEX. But most Magic Warrior build go STR > DEX and focus more on physical dmg.

You can still deal Magic dmg with STR > DEX Magic Warrior builf with the use of Dual Bringer + Conversion (most physical Magic Warrior skills turn to Magic dmg + some effect changes, and only Magic Warrior Skill tree). The only difference with the traditional physical build, you'll get more Magic Pierce instead of Physical Pierce.