>>18566791To be fair it's hard to unmake a good Pokémon - a lot of Dragons are cover legendaries, so chances are they'd be in Ubers regardless of their typing.
Looking exclusively at non-legendary Dragons, there's Altaria, Flygon, Druddigon and Dragalge all of which suck already, and pseudolegendaries.
They could have changed Dragonite's HA in Gen 6 and crippled it - Multiscale and being the only Pokémon to learn both Thunder and Hurricane were what kept it OU in Gen V.
That just leaves Garchomp, which couldn't give a shit about its ability. Hard to see how they could ruin Garchomp, short of Togekiss getting Moonblast or something.