I hate to wander back to this days later... But I was thinking about it, and remembered today that WRT has a prereq of one White Raven maneuver. So, really it's not whether it's worth you're one 12th level feat.
The question is "Is it worth your 12th level feat and a previous feat, used to gain a White Raven maneuver w/o a prereq?"
Then, if you do that.. You can only take Martial Study 3 times, and each time you take it you get the class skill associated with the school of the maneuver you picked. So you're in a sense also giving up a potential class skill, since you gain no skill when you pick up WRT.
And don't forget, if they don't have a recovery method when they take the feat, they can only WRT 1/encounter anyway.
Honestly, if you feel you absolutely must nerf WRT though... My best suggestion is simply declaring that no one can gain more than one extra turn with it in a single initiative round.
Really though... Playtest it and see how it works in practice. It's easy to abuse on paper, but a little tougher to wreak havoc with in game.