You're not alone, apparently the last update was to improve connection issues and matchmaking. I don't know who for it certainly isn't most of us - at least not if you're in the UK.
I can't understand how if I'm in a party of 6 from UK we get matchmaked with 6 Turks, 6 Italians or 6 Spanish???
It definitely seems the better your quality of connection the more advantage those with bad connections have.
So, sorry I can't answer your question I guess we'll have to hope a Dev comes out from behind his console and explains why its so bad. Trouble is they don't seem to give a **** what we think or they would have fixed it.
btw there must be more that 10 of us playing MW3 in the UK surely?? Shame they never get matched against us.
I know this is off topic but, any conformation of what BO2 will use as it's matchmaking system? I've heard rumors that they're going back to a modified MW1 era matchmaking system. Not sure how much of a solution that is or would be. But (for me at least) anything's got to be better than what MW3 is using...