There's quite a few spells and abilities which have downsides, or debuffs which have upsides.
The tooltip doesn't tell you that you're going to be set on fire, but the first time you use it you'll figure it out. And really, there are LOTS of tooltips that don't tell you everything they should. The Elemental Shield spells don't mention that they give you extra hp (which is huge), Boulder Smash doesn't mention that it leaves poison, Flurry doesn't mention that it hits 4 times (which is the entire point of the skill), etc etc.
