i'll be honest, the deck looks pretty solid - has a nice game plan, seems to flow well. however, will it actually hold up against other decks?
i've experimented with both cress and darkrai, both in their own respected decks. what i found was that they take a little long to set up, esp cresselia. at least with darkrai, in a solid dark deck, he can sit on the bench all he wants and he'll gather those energies, switch out, put them to sleep, if they're still alive, attack for a possible 110 damage. thats why dark decks will most definitely see action. the effect is just dangerous; that extra 50 damage is scary
cresselia, however, all depends on whom the deck flows with. i haven't tried it in a darkrai deck. so i'll definitely consider it.
cress on the other hand, alright attacks, however, it takes three to deliver 50, so i dont think that it should see much action in any case. MY strategy when i run cress, is basically leave on the bench as EARLY as possible, that way, if you happen to last a turn with your attacking pokemon, the excess energies will shift over the cress. then it can definitely pick up the slack. ( i think that was the intenton )
as for putting them both together, where a bare minimal damage is 50, although weavile is helping them, it still may be too too slow for comfort. thats just my opinon. but if you honestly want to see if it can last or make an impression in states, i suggest you play against those leading decks (i.e. magmortar and GG) and see how they work. in my honest opinion, your biggest threat are those two. they set up way way fast, as well deliver heavy damage. it shouldn't be an exact anti or lockdown for those decks, just try to hold up against them.
ake boundary would be a nice little one to add in, perhaps even another tgw (card disruption can definitely be an advantage for you). more MR STONE. i was running a solid dark deck, and i felt that energies would run out way way too fast for me. so if i were ever to play a late game, i'd lose.
i think you could lose a xatu line 1-1.
even a pachi/corsola start is nice, helps you get those basics out asap to start the beatdown
one other idea to help energy flow is swampert ex. if you use him, you'll need holon circles too
suggestions are limitless, all depends on personal preference...
one last thing to note: if you feel like you need the card, and can last without it, then drop it. don't be dependent or feel like you need it.
**to beat a fast deck, you either have to be faster or slow them down: i suggest card disruption and crystal beach (that slows blissey down a turn or two)
hope this helps, keep posting