the main problem is that if you don't need wormhole then you are farming too high of an MP level.
To be efficient you should be teleporting almost constantly or you might as well use lazybeam archon if you like walking.
I don't know, I find the boost to exp and Essence drop rates quite valuable in mp 7-10. I guess mp 3-5 to wormhole all over the place is more efficient still?
The boost in essence drop rates is completely negated by MP difficulty scaling.
can you do 2.5 more elite packs per hour in MP0 than in MP10? Then you can get more DE in MP0. (aka every single player out there)
The boost in XP is much less cut and dry, but really nothing beats fast killing. Once you are killing mobs as fast as you can get to them, efficiency is about how fast you can get to them. Once you are moving as fast as possible (constant wormhole), then efficiency is about how high can you tune your MP level before it slows down your kills per hour. Right now my kills per hour are only marginally different for MP0-2 so I do MP2 because loot, xp, DE, are all products of kills per hour. It doesn't matter that MP10 has a 510% multiplier you are killing 6x less mobs per hour.
Of course, none of this matters if you aren't having fun. Efficiency isn't the whole game, but upper MP levels aren't efficient for anything but uber/keys