No first-hand experience with Praxis, but they're often mentioned in the same breath as Shimano when it comes to great shifting performance and (iirc) they're the only two manufacturers cold forging their chain rings. While there's always the possibility that there's something wrong with the chainset, I think it's far, far more likely that there's something wrong with the set-up.
In addition to what revchuck suggests, I'd adjust any in-line adjusters to the middle of their adjustment range while the cable is disconnected and I'd peel back the hood cover to double-check that the stop on the end of the cable is fully inserted.