Blaziken isn't that broken, which is why it's UU. So no, blaze blaziken isn't uber nor would it ever be uber. Speed Boost JUST makes it go up one tier, but that's it. Seriously, does anybody know what the move Psychic is?
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Too be fair, banning a certain ability + Pokemon combo is nowhere as "complex" as limiting a powerful Pokemon to weak moves. Unlike moves, a certain Pokemon's ability is a permanent part of it. It's even more "permament" than alternate formes, which for the most part can be switched on and off on the same Pokemon.
Why must Blaze Blaziken be banned if Shayman Land forme isn't? A SHaymin can freely switch from non-uber to uber. Meanwhile, a Blaze Blaziken can never become uber.