I used Wax Key once, and I was mightily annoyed by it, in fact. Let's take for example some fort's prison area. You unlock one of the cells, and you get the wax key for it. So, then you open the next 5 cells with the key and forfeit the lockpicking XP that you would normally get for them. That's really some sort of facepalm design.
The perk that sets the pick to a position near the sweet spot is nice; I like Unbreakable a lot as well; and I like Treasure Hunter a lot. I definitely found more rare stuff with Treasure Hunter than without.