You forgot an important point, that makes Magic more powerfull :) Magic Missiles follows the normal Rules, that means that such a Missile enhances the Damage for each SL you make on a Casting-Test. After this, you can seperatly use all your SL's for the Rules of Overcasting. And i think, Wizards are...

In normal cases you get to your Strength/Endurance Test your advantage bonus. But as you says, attribut vs skill is a bit difficulty to win a test. and if you win it, the opponent gets another Test at end of turn to reduce the Stun-Condition. Ok, that turns into a fatique-condition. But in normal ca...