I play on my laptop and just couldn't adjust to playing with the keyboard and mouse (trackpad). WASD is fine for FPSs, but the need to be aware of my exact position in space while keeping track of the mouse AND being able to access all numbers at will just didn't work. In an FPS, you have a currently selected weapon that's prominently displayed at the bottom of the screen. Numbers are only used in an FPS when you switch weapons, and you can use the mouse wheel for that instead. Even trying to work with 'currently selected weapon' mode didn't work for me with AVWW since I had to look back at the bar to see what was selected.
Chris pointed me to the old fashioned aiming technique, where you shoot in the direction you're facing, and can shoot in diagonals as well. I haven't looked back -- I can now easily access all numbers and the game has become much easier to control. There's really no need for the mouse -- those few extra degrees of aiming don't make much of a difference since you can just reposition your character to achieve the same thing. What's important is that your brain and fingers are handling fewer things at once, so you become much more efficient. I can easily use almost all of the spells in the toolbar now.
BTW I strongly dislike tab-targeting mode. It's like auto-aim in an FPS, and to me it feels like cheating.