Waivers tend to take as long they need. DODMERB does not grant waivers, the commissioning source does. If you are waiting on a waiver for a SA, that SA is the one that decides on whether or not you will get a waiver. I am sure the SA you applied to will make all waiver decisions by 15 APR, as they will have decided who they want to admit or who they are willing to give a waiver to.
If your waiver is denied by an SA, there is a chance you can get it approved through ROTC.
Mohawk is completely correct and each commissioning source can act differently. DD received a waiver from West Point in less than a week, USAFA never requested a waiver and ROTC took almost nine months to approve.