Ideas to make Knockbacks fair

I have just thought of the perfect way to make knockbacks fair.

I'm talking about druids, shaman and yes even fire mages. These three classes can spec to have a knockback which knocks people off cliffs.

To balance this out, I think other spells should be able to result in people falling off cliffs too.

I propose the following:

Fear - Players run around randomly as they currently do, but instead of turning at edges, they run off.
Horror (Death Coil) - Same as fear
Blind - Players wander around aimlessly as they currently do, but also wander off the edges

All of those make perfect sense and are just as fair as the knockback spells available. I don't know whether or not polymorph should do it because sheep don't run off cliffs unless other sheep do.

An alternative to these measures would be of course to ensure that people being knocked back come back down to the ground before they would have fallen off an edge, and keep the other spells as they are.