I messed around with this some to give you some results, Ghost =)
I usually do my runs like this:
Act 1, a fairly comfortable MP5, as the enemies are relatively simple and mob density is low
Act 2, MP 2/3 (screw A2)
Act 3, MP 3/4 (mobs are a bit tougher than A1 mobs)
Did my 5 runs in Act 2 at MP2. I chose MP2 partly to make it quick and partly because I hate A2...okay, so thus entirely to make it quick. I chose Act 2 because...well, because I hate it and was most interested in how to make it specifically as efficient as possible ;)
Runs were 9, 12, 12, 11, and 9 minutes. Closer to 11.6 than 9.5 (though I'd have rounded it up even if it wasn't), so that gave me Type 7.
Type 7 suggested MP6, and suggested that runs would likely average about 23 minutes. I was skeptical (and scared) but gave it a go:
My run took 39, which is a fairly big gap. This might actually have been a reasonably fast run for me, because I found the keywarden quite quickly and just needed to go find stacks, and thus wasted no time on extra packs while looking for him.
Of course, I did spend a short amount of time dealing with 2 packs sitting on top of the Dahlgur Oasis waypoint (I did not even get a chance to move before they were on me). They looked like this:
Yellow Snake Pack:
Frozen, Waller, Nightmarish, Vampiric
Blue Shaman Pack:
Frozen, Jailer, Plagued, Electrified.
This didn't waste much time due to how ridiculously quickly they'd murder me. Granted, I'm not using the most mobile build there is, but even being able to vault and smokescreen out of CC wouldn't have mattered with that much of it and with it being right on the waypoint with no room to work with.
I let them kill me 3 times before giving up because the Vampiric snake guy was at 100% health from all the killings, and headed to the Path waypoint instead.
Found the key warden almost immediately, managed to avoid pulling him, and made note of his location. Then I gathered stacks. Individual packs went much better than I expected. I did not die to any of these packs, nor to the Warden.
I actually expected to take a lot longer than 39 minutes (and possibly to be unable to do it at all), so even though I will not try Act 2 at MP6 again any time soon, I am happy that I did this.
Also, he dropped my key, so there is that! ;)
I think part of the reason it's so much slower for me at MP6 than just the health increase would suggest is that I'm not as comfortable skipping packs. I need more space to move to deal with the elites and their ground effects which pile up when they live so long, and having those little guys getting in the way while fighting an MP6 elite can be problematic. Also, the tendency to encounter multiple packs right on top of eachother is tougher to deal with at higher MP levels. I'd have laughed (well, comparatively, it would have been doable) at those two packs on that waypoint on MP2.
Maybe you can find a way to account for things like the little damage increase enemies get for each MP level?
Oh, and I think I will start running A2 at a higher MP level than currently, regardless. =)
Oh, if Armory is still showing my Nat's hat, it's outdated. I have a little more damage than that. The build is right, though.
Edited by Tiakatt#1643 on 10/26/2012 12:22 PM PDT