Now hold it. Basculin in UU or lower? I don't get it. Now, I'll admit, his movepool sucks to such an extent that there's only one really viable set, (Aqua Jet, Waterfall/Aqua Tail, Crunch, Double-Edge) and he is rather frail. However, once you get past that, you see a rarity: a Water sweeper. Heck, he has not one, not two, not three, but four Abilities, all of which a good sweeper would kill for. Heck, who WOULDN'T like a choice of Rock Head, Adaptability, Reckless, and Mold Breaker? Give him a Choice Band, and let it sweep late-game. Oh, and I typed this on my iPod. That's how strongly I feel about it. XD
Unfortunately, this guy just isn't cut out for OU...
Rock Head is solely useful for Double-Edge, which is much, much weaker than a STAB, Adaptability Waterfall.
Adaptability is the only thing that can help Basculin compete with Azumarill, as it allows it to carry a strong Surf, as well. Even then, it's not physically as strong as Azumarill, which is vital for a metagame infested with Excadrills.
Reckless only helps with Double-Edge. Adaptability Waterfall is still more useful, with better neutral coverage and STAB.
Mold Breaker mainly helps against Water Absorb/Dry Skin users, who are, besides the rare Water Absorb Quagsire and Dry Skin Toxicroak, usually resistant to Water-type, regardless.
Therefore, Adaptability is really the only viable ability. And while it does allow Basculin to run Surf for physically defensive foes, its Special Attack stat is not impressive, and it does not have the Attack stat to OHKO Excadrill with Aqua Jet. It also does not have a good way to take down the multitudes of Ferrothorns in the metagame besides Hidden Power Fire, which doesn't have the base power to take it down, anyways.
It's just that the main thing holding Basculin down is its inability to take down Excadrill assuredly. Azumarill is the better choice, as the ability to revenge kill Excadrill is just way too hard to give up.
Oh. And besides its defenses being terrible compared to Azumarill, its Speed is not good enough for the metagame, as well. 98 base Speed is reeeeaaaally trollish...
lol. Outclassed by Azumarill. That's kind of embarrassing.
-Zane