Please compare this to Air Blitz
This vs Air Blitz
Cost: 9|8
vs 9|8
(drain remainder)
Duration: Permanent vs 1 turn
Effect: Almost double fielded damage vs Doubles fielded damage
The drain remainder part of Air Blitz's cost is due to a non linear self-stacking effect so it can be ignored.
What we a left with is that Stampede is obviously superior to Air Blitz for no good reason.
Summary: It is the duration that is the problem. Draining all
will not solve the problem and is not a useful addition.