How to Get the Gnomeregan Key
In Gnomeregan there is a key, just like in Scarlet Monastery. But this key is more of a shortcut than something that is needed to unlock content in the game. The Workshop Key can be used to open the back door of Gnomeregan and allows you to skip part of the instance.
This key drops from the boss Electrocutioner 6000. Of course, Rogues can also pick the lock of the backdoor too at level 150 lockpicking.