I've seen 2 Mewtwo included into most Blastoise variants as it can trade well with opposing Mewtwo and Keldeo. If your opponent sets up a very large Keldeo EX, then you can punish it with a well timed Mewtwo EX. I would like to see at least 1 Mewtwo EX included into this list. Also you'll have to be more careful with the Tropical beach drop as Virbank city gym will be popular to counter it and deal more damage !
I moved the thread to the TCG Deck Reviewing subforum of the Pokemon Trading Card Game forum.
Once opposing players catch onto the Ditto strategy, they'll be more likely to take it out.
I'm talking about the fact that it'll need 4 energy to do that 200 damage, and even with Blastoise that can be a pain to consistently do due to a limited energy supply in the deck and the recovery limits of Energy Retrieval.
I have minimal experience with Blastoise/Keldeo builds. Closest I've come is a BlastCatty build in 2009, which had a slightly different energy mechanic because of the Platinum Blastoise's power. Though I am familiar with how the Rain Dance mechanic works after using it frequently in casual play over the years.