I was about to agree with the "remove the damage from Teleport" suggestion, but I remembered that probably exists for a very good reason - to not let you teleport neutral NPC's like guards and merchants away from locations they're watching, thus letting you exploit things.
or Vault or Expeditious retreat or ...
Is the Teleport the only spell which everyone must have or be doomed?
Vault isn't a teleport spell, I think you mean Cloak and Dagger and Tactical Retreat. So all right, there are alternatives... but as those are self-teleports, not Teleport Other, which would mean more people would need to invest into self-teleport skills.
All I'm saying is that I'd think really long and hard about all the consequences of cutting the range of Teleport.