Quoted By:
I don't know what goes through Gamefreak's mind when they do stuff like this. It has a cool design, a unique typing, it's the only dragon with Scald and Focus Blast, the one of the only things in the game with Toxic Spikes+Phazing move (only other is Drapion,) it has Poison STAB for Fairies so any that aren't Mawile risk that if trying to switch into a DM, it's really just pretty cool. But it doesn't have a good ability; it technically does, but you can't get it because why not. Its HP and Speed should also be a bit higher.
It's almost good, but it's not. And it probably never will be, like the dozens of fully evolved things that are just an ability or few stat points from being good and will never get retconned (+10 SpA to Azumarill is an important change though.) It has a chance if Adaptability gets released but that seriously may never happen.