We have already noticed these differences.
It seems you can't estimate your payout only by taking some dudes' payouts with the same hashrate.
There are so many parameters that you don't know from the server: accepted shares, stale shares (and btw do you submit your stale shares?), discarded works, gpus used, PSU, drivers, OS, settings in config files, mod miners, network connections...
I've been mining on 2 different servers (eu and east) these last days: I didn't notice huge differences (same coins mined at -almost- the same time on the 2 servers). I may be wrong but I don't think the differences depend on which server you are.