How much is combat efficiency of the phatansmal thief?

[ayvango]

In the 5th level slots it competes with baleful polymorph and other save-or-die spells. It could not ruin opponent with in one action: wielded weapons could not be pickpocket. But it could spoil many evil plans and lasts level per round, so it has many tries.

[Hellpyre]

It provides a somewhat efficient means of dealing with a spellcaster (by liberating a components pouch or Divine Focus), but is otherwise only useful if you know what a given creature is carrying with it. In combat, the time it takes to cast and then steal makes it inefficient, but when ambushing it can be useful for its slot. I recommend it more for NPCs than PCs.