I agree, these guys beat anything... as long as they dont face donphan of course, nothing that lanturn can`t solve anyway.
Simisear or Samurott can take the 6 prize cards in just 3 turns against them, unless mew stars the game, I find it quite difficult for it to win, the jirachi and shaymin combo might work if you have enough luck... but is luck after all.
Would you mind telling me how you are going to take 2 prizes per turn? Also no one plays simisear and samurott is a stage 2 so all mewgar has to do is get 2-3 engergies attached to it and use hurl into darkness before you can get samurott out.