More players generally only dilutes your MF
I'm glad someone else tweaked onto that one, its been bugging me for awhile. Why does other peoples MF affect mine in a game with instanced loot? Why does a supposedly multiplayer designed game actively punish you for playing with other people? Why does balance matter in a segmented game with few persistent elements? So many things are totally at odds that it feels like they just don't have a handle on any strong overall design goals.
You can tell they really didn't think a lot of these changes through. Many of them were made in the latter half of their pathetic version of beta that tested essentially nothing other than the battle.net infrastructure. Overhauling the entire rune system a month before release without testing was another head scratcher.