It's easy to isolate what's broken. Drizzle isn't broken with anything else, so it's the Pokemon that are the problem. Three Pokemon: Kingdra, Ludicolo, and Kabutops. There has never been any indication of Qwilfish, Poliwrath, Gorebyss, or Floatzel being broken under any conditions, nor for the other 12 fully-evolved Pokemon with Swift Swim. Restricting 19 Pokemon for the sake of 3 is not what fits with Smogon's minimalist bans policy.
Exceptions aren't something that are detrimental in the slightest unless they create a slippery slope. Any exception judged to be reasonably unlikely to cause a slippery slope should be used whenever it works, to fit with Smogon's minimalist bans policy. That determination matters based on what sort of ban it is, not what will happen as a result of the ban. There is no issue that is minor enough that we should be willing to have a worse metagame for it for the sake of preventing an exception and gaining nothing in return.
I know that Kabutops, Kingdra, and Ludicolo were the front runners, and I KNOW that all the other swift swimmers weren't tested with out those main three gone. But seriously.
Quilfish was argued to be like another version of Kabutops in fourth gen, just with poison typing. I could EASILY see him taking Kabutops place, although the explosion nerf may not be as good, he still has SD, and Waterfall, and Aqua Jet, and Thunder Wave, Toxic Spikes, and Spikes. Not to mention poison typing to absorb toxic spikes.
Golduck has the same Special Attack and Speed as Kingdra, and can run an efficient calm mind set, or do the same thing Kingdra does with Choice Specs Hydro Pump. Albeit, with pure water typing and lack of dragon stab, but still a dangerous threat.
Poliwrath... Oh god, are you kidding me? Belly drum + Swift Swim? Really? You want that? Or how about Bulk Up?
Omastar is still dangerous, although slower than the average swift swimmer, it has shell smash AND 115 special attack and a decent move pool to boast is still a threat. Also has access to swift swim spikes, stealth rock, rapid spin, haze, knock off... Still one heck of a threat even if he decides to go supportive!
Gorebyss has been causing problems NOW with shell smash, and in swift swim, I am sure it would destroy just as wel, and same with Huntail.
Floatzel although only running off 105 base attack, Theoretically he could quickly take the spot of Kabutops/Quilfish if they were banned. Or run more of a supporting baton pass in rain set, that could prove quite powerful. And could quickly take a valuable spot.
Seriously, when I look at the list, there may be 5 that I can count that might be not a threat. Luvdisc, Lumineon, Armaldo, Mantine, Beartic... Seaking... I really don't want to ban those above mentioned pokemon so I Luvdisc might see some use in the rain. No, I don't care about that. Out of these 6 the only one I care about is Armaldo with Swift Swim.
The theory was the cascade. Most of the majority felt that those other pokemon I mentioned above would take the place of Kabutops and Kingdra and Ludicolo. And FFS... if those 3 were banned and those above mentioned threats didn't take their place? My mind would melt.
