The phoenix does lose polymorph as part of a splatbook-wide errata which basically removes all shapechanging powers from monsters unless it is integral to their fluff.
The crappy DC was partly why I mulled over the monster of legend template. Between the +10con and +4 DC ability, this raises the final DC to 31 (or 33 if you give it ability focus), much more respectable but the small radius is still an issue.
Else, I can't really see how the phoenix fights. Holly berry bombs are cumbersome to spread and do pitiful damage, while the rest of its SLAs are either defensive or healing in nature.
And wow did it take a lot of time and effort typing out and organising those entries. My respect for all those thread handbook authors just went up a few notches!