He only gets to use it once, right? He can't recover the maneuver, and he can't use it in multiple encounters, right?
7,650 gp for one double-full-attack seems okay... if he could recover it, or if it worked in every fight for 1 hour, that would be crazy strong, but just once? I dunno.
It's Martial Script stances that bug me more, since you can initiate them once and stay in them all day. Assassin's Stance for my rogue? Yes please!
Cheers, -- N