Delphox EX and the new, Darkness-Type Greninja show some promise, but aren't without hang-ups.
Delphox EX: Psybeam is mostly so the card doesn't have to sit dead if it can't afford Wonder Flare; 20 and Confusion for [C] isn't "bad" but it isn't "good", either. Compare it to other Pokémon with similarly priced attacks (there are about a dozen) and you notice that if that if the single Energy attack is the primary reason they see play they are significantly better; multiple Energy card acceleration, single Energy acceleration with damage, more damage to the Active, more damage to the Active with a nifty effect like discarding a Special Energy from the Defending Pokémon, damage to both Active and a Benched Pokémon, etc. Looking to the future, this kind of attack also makes it unlikely we'll get the First Turn Rules restored anytime soon (remember, the problem wasn't attacking first - the problem was attacking for damage first turn).
Wonder Flare is good but not great; right now we don't have a good way of guaranteed the opponent has an Energy in hand. Do we have a way to even see your opponent's hand that isn't a Supporter or an attack? Even if you use effects that force your opponent to draw, we have a similar issue with the few exceptions being random and apt to give your opponent a net decrease in hand-size (N and Red Card). I can still see this working, but mostly because Delphox becomes another big, Basic Pokémon-EX that can take the brand new (in Japan - not out here) Fire-Type support. With Blacksmith and a Double Colorless Energy you can power up Wonder Flare in a single turn... but you can do that with other Pokémon as well.
Greninja: Catch-22 here; if you rely on the protective effect, how do you keep using it turn after turn without having a Frogadier? That matters because if you have anything benched, not only can Pokémon Catcher (on "heads") and Lysandre (at the cost of your Supporter), but even Escape Rope is all but guaranteed to take a Prize and potentially break your "defensive" lock. This is in addition to all the Pokémon that have attacks which ignore effects on the Defending Pokémon that reduce damage, Abilities that place damage counters, and Hypnotoxic Laser. Related is the concern is that even if you're able to spam Devolution Spray to abuse the effect (total of eight "invincible" turns), spread damage will become a concern. Obviously if you do only have a single Pokémon in play, G Booster can win the game in one shot.
The attack is another concern; it isn't abysmal but it isn't 2HKOing the average 180 HP Pokémon-EX which means it needs boosting or else there is a risk you won't win even with eight turns of "invincibility".