Dark Void broke Darkrai. - Wrong.
Air Slash/Seed Flare broke Skymin - Wait what? No.
Outrage broke Mance in 4th Gen - Mence was never broken.
Swords Dance breaks Garchomp in 4th Gen - No. Swords Dance + Yache plus the fact that you either had it or lost broke it.
Draco Meteor broke Lati@s in 4th Gen - No. Soul Dew did.
Recover broke Deo-D in Gen 4 - No. It wasn't even broken there.
See where I'm going?
Because those two have no correlation.
Is Infinite Rain, Boosting Water-type attacks by x1.5, a part of Swift Swim, Kingdra, ect?
No.
Is doubleing the speed of Kingdra, ect, a part of Politoad?
No, it is Swift Swim, which is a part of Kingdra, ect.
See the problem here, the two are broken in tandem, but not as standalone. Rain has not been proven as broken standalone yet, and Swift Swim is certainly not broken under self-supporting conditions [Rain Dance].
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Meanwhile:
Is Speed Boost a part of Blaziken? Yes
Is HJK a part of Blaziken? Yes
Is Flare Blitz a part of Blaziken? Yes
Is coverage moves to hit all of its counters a part of Blaziken? Yes
Is Swords Dance a part of Blaziken? Yes
Is the ability to be a mixed sweeper part of Blaziken? Yes
See the difference? Blaziken is banned because Blaziken is broken... as Blaziken. Speed Boost is a part of Blaziken, Swift Swim is not a part of Politoad, nor Drizzle a part of Kingdra.
The only way a complex ban would come into force is if Speed Boost was a broken ability in its own right, like Moody was. Ninjask and Yanmega are not going Uber anytime soon.
Banning Speed Boost on Blaziken is like banning Dark Void on Darkrai, or Outrage on Gen 4 Mance, or Air Slash on Skymin.
Drizzle + Swift Swim is combo banned because they are broken in tandem, but not alone. [Well, Drizzle might be, we'll see how Round 4 goes]
Speed Boost was a part of Blaziken. Everything broken about Blaziken came from Blaziken. Therefor, Blaziken was not fine, and there is no grounds fo a combo ban.
Wait, so by your logic, if Blaziken got a dream world ability like, say, Iron Fist or , it would still be broken?
Banning Speed Boost on Blaziken is not at all like banning Dark Void on Darkrai or Outrage on Mence or Air Slash on Skymin. You know why? Because unlike all of the other things you listed, it is an ABILITY. Key word, ABILITY. The ability to take its craptacular speed to new heights entirely. The reason that Speed Boost Sharpedo/Ninjask/Yanmega aren't broken is beacause they have poor offensive stats, craptacular defenses, and in the case of the latter two, a 4x weakness to Stealth Rock. Blaze Blaziken's best shot at outspeeding anything in OU was agility which its fragility and weaknesses to Water/Ground/Flying would not allow it to do easily. Speed Boost Blaziken made this a non-issue because it required NO SETUP. It didn't require the use of a moveslot. It didn't require it to switch into something faster. The ability itself is broken ON BLAZIKEN. Stay with me here, ON BLAZIKEN. If Rampardos got Speed Boost, it would be broken. Wouldn't it? If Feraligatr got Speed Boost, it would be broken, wouldn't it? Speed Boost itself is a busted ability, the only reason it wasn't banned before was because it was on bad Pokemon.
On the Drizzle + Swift Swim issue, I was using that as an example of the first ability ban. You missed that point entirely.
Also, just listen to everything SJcrew said.