How about make sure every spec has at least a 20 second no resource interrupt/kick that will reset the cooldown on mob abilities.
Doesn't have to have a lockout (2 sec at most), doesn't have to have a silence at all, just a button you can push to kick a cast bar.
Give it a short range, say, 10-15 yards max for non-melee classes.
If it doesn't work on players, fine, who cares.