Yeah, Dialga's return hurt this deck alot. I haven't played it in a CC's yet; I've played LuxChomp twice and DialgaChomp twice, but not Palkia. Having Champ and Dialga as virtual autolosses wasn't a problem before, but now it definitely is.
Like DarthPika said, however, HGSS looks to give some serious help. Palkia/Garchomp (which also handles Luxray really well due to the non-X's 80HP) becomes a powerful sniping/locking deck with DCE, and Pixies can be searched en mass with Pokemon Collector. And Ninetails might help Fire decks enough to scare Dialga out of the picture (maybe, Dialga's good enough to handle a lot of Fire and Quagsire 2HKO'ing even Charizard makes it possible to easily win). I believe that Palkia will most definitely be better then, though. The format is just shifted against it for now.