The advantage is in "dancing" and such and avoiding keeping creep-blocked.
With a mouse you have to click behind you, then click the person to attack someone, so you keep having to move back and forth.
With using WASD and mouse you have your mouse free to keep your cursor on targets while you move with the keyboard.
why does the arguement always come down to that if you don't want the game to go at 400 APM, then you want the game to play itself? Why can't you accept that there's middle ground?
It actually makes the game LESS micro intensive. as you're holding WSD keys instead of constantly clicking back and forth with the mouse! :/
WASD controlls lower the APM. High APM is a nessisity in SC because you're constantly needing to select units, tell them to move, then tell them to attack. Since you're using the WASD for your hero to move you cut down on half the clicks, actually.
And to be frank.. Demigod is meant to be a competitive game. People who micro good will have an advantage on people that don't. It doesn't mean it's going to be fun for those that don't.
I understand some people don't like WASD movement. Some people in Guild Wars didn't, but know of those people topped the ladder.

That doesn't mean the option shouldn't be there.
WASD+moues is superior input for controlling a single player in ANY game, no matter what genre it is. Sheesh do you people like playing FPS' on consoles or something?
When controlling a general, yeah for your minions you would be selecting them and clicking with the mouse only. But then you might be pressing the hotkey to select your hero only and going to WASD. I know that's how i'd do it.
Again, I'm not saying click-to-move should be removed, but I STRONGLY feel there NEEDS to be WASD control for the Demigods.