Having played against Belly Drum Azumarill and used it a bit myself, I find it surprisingly lackluster. It is a decent sweeper, but I find that Choice Band just does more for your team, and on a consistent basis as well. Belly Drum Azumarill can not risk checking attackers like the CB set can because if it takes any damage you jeopardize your opportunity to set up a Belly Drum in the future. That sacrifices one of Azumarill's best attributes: utilizing its great typing to pivot and check threats for a team. It just seems a shame that you can not use a Dragon-immunity, Fighting-resist, and Water-resist off of decent bulk for a team because you shoehorn it to safety so it can pull off a Belly Drum. Azumarill is put to a lot better use firing off really powerful attacks off of its resistances consistently throughout the match than setting up off its resistances for one-time and only one time in the match. That one time isn't from you winning of course :p