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Sorry if this is a stupid question, but shouldn't the cutoff for dropping megas be lower than normal mons? You can only use one per team, and that's why their usage is so low compared to other pokemon.
Mega Alakazam is banned in UU, so if the usage stays that way it will drop to BL. I think Celebi is also banned, but i'm not quite sure.
Also:
Why
There's a silver lining. I'm looking forward to the next tier shift.