Personally I dont think this has a chance of being implemented. In the mounts thread, Wiz stated that one of the problems with horses (or the like) was the automed feature, so its unlikely that he would approve of an automed by itself. Also, I would think this would change game mechanics (just a tad) in the sense that casters on raids will have more mana since they're standing most of the time and the pulls are constant. One of the most basic tactics on raids and even groups is to have the casters stand on the pull, and I doubt that this will be changed. Casting classes would also be easier to DC.
But then again, I'm no one of authority so dont take my word as official, just trying to put some insight into the topic
I always pull past casters and they never get hit... you need to make sure you have a good puller who casts a nice agro spell (snare) or atleast hit the mob a few times before you pull it back to the group. It always seems to work for me. (or if you have flash of light it'd be better since it no longer makes them run in random directions)