i expect to see a lot of not so good players playing 2-2 just like a not so good player might play 2 gardy x's, just because noobs think by adding as many expenxive cards as they can it will be better even though it's not needed, 1 tsd - 1 nm works better in some decks for function, than 2- tsd but you still see people play 2 tsd in every deck if they have 2 because it's glamorous
You didn't actually read Cresselia, did you? There's nothing in it's text about "You can only use one Full Moon Dance per turn", meaning you can move two damage counters per turn rather then only one.
Double the damage manipulation = double healing = double damaging = twice as good. You already play a solid pokemon searching engine. Why are you not doubling your effectiveness with the Cresselias?
Say you're playing Magmortar. They do 40 and spread 20 to two different benched pokemon? You realize you get to place a third of their damage right back onto anything you want, right? You realize this means you can fully protect a benched pokemon if you need to, right? You realize this allows Gardevoir SW who does 60 damage max per Psychic Lock to do effectively 80 damage when needed, right? (opening up KOs on Magmortar LV.X, for instance). You realize this gives you amazing ability to control who gets KOed with Bring Down, right?
Gardevoir PK is probably a bad idea to help Cresselia, 'cause Cressy's attacks frankly aren't important. You don't care if Cresselia can heal itself with a stadium out, 'cause it likely won't be active. You don't care if Cresselia can take two prizes at once (early game, this is), 'cause you'll want to invest energies into something that can take Double Rainbow and absorb over 100 points of damage. You don't care if Cresselia can heal 1 pokemon on the bench completely, 'cause it's not difficult to get out another Gallade or something during the mid game, and it is too vulnerable to be active during the late game. So really, it's just the power you play it for. And considering how easy it is to get out Cresselia LV.X (a
BASIC LV.X), there's no reason to not take full advantage of it.
It's not, "Oh, let's add two 'cause they're pretty!" It's more, "Oh, hey look. This card has a useful power, that can completely flip my opponent's efforts back against them. And I don't have any problems getting them out? And I have something that can switch them out of the active spot right away? And I can play a stadium to have free retreat on everything anyways? Why AM I not playing this?"