Did you follow the pad break-in procedure that should have come with the pads? I've heard that this is critical for Axxis Ultimates. (and other hi-po pads) The break-in consists of just what you mentioned: usually about 10-hard stops to get the pads smokin' hot, and then allow them to cool.

Give this StopTech article a read. The topic is "warped brake rotors", but it really talks a lot about pads. Good stuff.