Gyarados can switch into Azumarill a lot from my experience, with that Intimidate just halving his attack, but it's more a check than a true counter. If you REALLY wanna scare it, you can do a lot worse than Magnezone, but even that can't take too many AJ's, would have to be a revenge switch rather than a standard one.
Blastoise and TFlame core seems pretty solid, though that electric weakness. I like Dugtrio as it can switch into the predicted Thunder/bolt (but not much else) and trap the opponent with it's ability, destroying them with super-fast Earthquakes.
Also, if your Blastoise isn't running Rapid Spin, then I suggest picking a spinner up. It's crucial to keeping Talonflame alive.
Shadow Ball > Pin Missile on Jolteon nowadays Donutman.
As for Pixilate Sylveon, Fairy type Quick Attack is kinda awesome, if not a little weak. Certainly polishes off those faster dragons nicely.