I was a bit put-off at first playing the D3 beta and having to click-control my character. (I hadn't played D2 for a LONG while)
That being said, from a design standpoint, isometric view and WASD together are just awkward. So, what, does W make my character go North? A = West, D = East, etc.? With WASD sure, you have an additional control scheme, but it comes with a reduced freedom of movement. (8 directions)
The reason WASD works so well in 3rd and 1st-person is the ability to set the camera behind (or as "your" eyes). Also, your movement or direction in 1st and 3rd-person isn't controlled by keys, it's controlled by a stick (precise) or a mouse (even more precise).
Implementing WASD would compromise the player's control in an isometric game. This is incontrovertible. Blizzard may compromise with its player base on some issues, but certainly not on game design. So unless you expect them to turn Diablo into 3rd or 1st person (if you do, I don't want to know you) please, give it a rest.
Enjoy the game for what it is.