I think it was done so there was actual reason to PLAY a Transmuter.
Pre-patch, there was 0 point having a Transmuter in your party because you got 100% of the benefits from a Hireling in camp handing out Stones and doing your crafting.
To say nothing about having multiple hirelings and companions dishing out multiple stones to party members.
Also Transmuter isn't Wizard's weakest subclass when Illusionist exists.
