I doubt the 2,500 MP cost will be the final number.
I expect they’ll make adjustments to both the MP cost and duration in patch 7.3.5. Specifically, I think the MP cost for melee will be reduced to around 2,000, and the duration will be restored to 3 seconds.
This makes sense because tanks really become unstoppable rampaging bulls when they reach 100% Battle High (Frontline).
Otherwise, melee will remain too fragile.
Unless they also plan to significantly increase passive damage reduction back up to 50%