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If the egg has a shiny value of 2172, I'm afraid you have the wrong guy. My shiny value is actually 2712 and I inputted the wrong number into the database.
What's everyone's opinion on Focus Punch on Sub + 3 attacks M-Mawile? She learns it through TM in Gen IV and is an option to hit any Steels that give her trouble. The only downside is that it doesn't have a use unless you are behind a Sub or they are switching out.
You won't be able to use recovery moves (although Regenerator is fine) as Assault Vest puts your Pokemon in a Taunt-like status where you cannot use any Status moves.
The current English translation patch uses greatly for a two-stage increase, since using Swords Dance (still a two-stage increase) "greatly" increases Atk.