It never should have been a part of mage gameplay
Why did mages get everything that everyone else had?
Chameleon and invisibility = Sneak
Open Locks = lock pick
Isnt it enough you can conjure weightless weapons, conjure pets, throw fireballs, breath under water, teleport, and heal yourself?
The problem is lack of alternatives which, in a RPG, is always a sign of bad, limited design.
BTW, I think the "open lock" spell was too lame and I'm not sad that it's gone but other characters should be able to open
low level locks in other ways
Bring back the bash lock option... this way a warrior can open them with a few hits or a mage can throw destruction spells at them
Only high level locks or particularly strong doors should be in the exclusive realm of thievery thus making lockpicking a viable and useful skill