I love teleport, and don't want it to be changed because:
1) NPC can also use it against you.
2) there are different skills that self teleport at big range (1 for rogue, 1 for hunter, 1 for warrior), or small range (rogue again), or swap character that you can use or npc uses against you.
3) it is pretty usefull to TP out of dangerous surfaces
4) or to bring range npc next to your warriors
5) you can fortify against it.
so basically it is for me part of the whole combat mechanic.
The real problem in my view in the situation you described is that you can TP a npc on a platform from where he cannot move anymore. The issue for me is in the design of the zone, not the teleport spell in itselfs.
