Why is mp recovery useless?

doublepost aside, i had been saying this quite a bit actually, both here and on sw, in various threads. But the thing i felt with it is that even w/o the "combo" with drain, since most of us use % hp pots like honsters, we already use less money doing mp recovery. The only real problem i had when i used it was that it takes a little bit longer then a mp pot, and that can be a inconveinence. I'd still rather have maxed barrel, but mp recovery is still useful.