It only works against Cressy without Twave, and is overall not the most amazing idea.
Cressy is indeed one of the best switch ins, but it still takes roughly 80ish-90ish% from a Fire Blast followed by a Draco Meteor, or a Dragon Rush/Crunch followed by a Draco Meteor or vice versa... it only needs to have taken a bit of previous damage for it to go down. And apparently according to Hipno Cressy is really easy to damage. *shrugs*
Also, you don't need to predict that much with this guy -- most of the time you'll just start with Draco Meteor, since that move followed by Brick Break/Crunch/Dragon Rush/Fire Blast will pretty much everything except Blissey, Cresselia, Bronzong, Heatran, and Jirachi, and they can be taken out either with prediction, or damaging them slightly first, seeing as how Draco Meteor followed by X does like 80% to all of these guys anyways...
The problem is that once your opponent sees Life Orb damage, they'll know its Mixmence (or should know). It's a good bet they won't keep in Jirachi or Blissey or whomever to take the following hit -- they'll switch to something to soak up the predictable Fire Blast or physical move. That being said, if you have good prediction skills you can slaughter them.



















