[quote=@KabenSaal]
<Snipped quote by Lugubrious>

Diablo 3 let Monk though beta test with around 2.1 attack speed. Then, about a month down the line, they nerfed it to about 1.4 attack speed, causing massive drops in dps and screwing over farming routes the game over.

How this is relevant to Moku should be obvious. You let her Mirror of Yata though character creation,  and a spar with that Semblance used, before thinking about nerfing it at all.
[/quote]

Yep.  I wasn't truly aware of how powerful it was until you said it pretty much couldn't be improved, though.  Fortunately, writing in this downside to an otherwise perfect semblance wouldn't posthumously interfere with the outcome of your sparring match, since its resolution was within the guidelines of the updated semblance.  This change doesn't screw your character over, far from it; it gives the rest of us a chance.