Use Return in Azumarill's last slot; alongside Waterfall it gets near perfect neutral coverage, bar hitting Empoleon who isn't common and is hit by Superpower anyways.
iirc Drifblim has access to Charge Beam; I'd use that instead of Thunderbolt. The SpA boost may come in handy at some point, and Drifblim dosen't exactly have the best attacking stats.
You can just use Haxorus; it's a solid DD Sweeper and it evolves before the E4. If so, use Dragon Dance / Brick Break / Earthquake / Dragon Claw.
My new mixtape is fire///