Turbo Palkia is definitely S-tier
I've finally completed my idea for a Palkia EX + Manaphy deck and so far it every bit as good as I'd hoped.
Here it is: 2x of every card-
Palkia EX, Manaphy, Misty, Pokemon Communication, Giant Cape, Poke Ball, Professsor's Research, Potion, X-Speed, Leaf
Use Pokemon Communication and X-Speed/Leaf to try and ensure that you can lead with Manaphy and have Palkia on the bench.
Use Giant Cape and Potion to try to get as many uses out of Manaphy as you can.
By the time Manaphy has used its attack twice, Palkia will be ready to go with at least 4 energy on the following turn.
As is usually the case, Misty flipping any heads at all will usually get you the win.
About 30% of the time, you'll get a bad deal and the deck won't work as intended. However, this is no different than Mewtwo decks not getting Gardevior in time or Celebi decks not getting Serperior in time.
In some ways, Misty flipping heads makes up for that.
I've had one game so far where I opened with Manaphy + Scarf, Palkia on the bench, on my first turn had a Misty that flipped two heads, and hit them with Palkia's Dimensional Storm on turn two lol. To make it even better, it was that annoying new Darkrai / Weavile deck lol