For spending a mastery you should be getting more than just a tech slot. It's kinda silly to use the rank for just that. So I won't mind seeing you get something a little "thicker" for the effect if you intend to keep it that way.
Personally? I'd recommend getting it earlier and as PART OF your mastery that it would reduce the cooldown. You just have to shift around some things to make that work.
The Lord of Nightmares spoke to the God of Dreams, this small child or so he seemed, and bid him the question of his sins,
Head of Public Safety Tsukimiya arrives in Hueco Mundo, intent on bringing justice to the criminals who have fled to the desert realm hoping to evade the long arm of the law. She finds what she is looking for in the throne room of Las Noches...
In an attempt to fill the vacuum left by the Queen and Primera's deaths, Segunda Espada Levi Grisha makes a play for the throne and gathers the Hollow-Breeds in order to stake his claim.
Meanwhile, a Shinigami assassin on an unsanctioned mission strikes at a hospital, aiming to rid the world of the Quincy queen's newborn children. Several Quincy rush to the queen's aid as Lieutenant Ogawa escalates the hostilites between mortals and Shinigami.