Because you are doing it wrong. At 110k DPS you should be running MP1 at the most. I am using the Act 1 profile and I average 45 mil an hour on MP2. 165kdps base/220ish buffed. And frankly even at that I should probably be on MP1 just for the speed factor. It doesn't matter whether or not you can actually kill something on any MP. My char can kill stuff on MP6 or 7 just fine. It's the speed with which it does it, and your char can't kill fast enough on MP2, hence why your numbers suck so bad.
Also, more goes into a rating for a profile than just it's XP/IPH. There are things like stucks, bad routes etc etc that go into it.
are you running a TR build? if you aren't then your point is obsolete. And second of all, i never said i had problems with killing them. Killing them fast is easy. The problem is mob density. There isn't enough of it compared to the profile i was running earlier.