I think you guys might be morons myself.
There's a very good reason why cresselia isn't that good anymore.
Scizor
Giving scizor bullet punch in platinum sky rocketed his usage, and with that came alot of scizors with x scissor. The only way cresselia can hope to compete is with HP fire, but that invites ttar and weavile to stomp on you all day.
cresselia has a very marked weakness and can't cover them all. She gets fully countered by a couple of pokemon without the right set, and the issue is that alot of those counters are on teams together.
with that said, cress is still very good and i personally have her on my team, and I wouldnt have it any other way. I just have infernape to cover scizor