Surely, it's not the mouse... I'm using a Logitech Anywhere MX™ laser mouse ( I have a glass desktop and require a laser) and have never had an issue with it.. excepting that I wore out the buttons on the first one and replaced it with another one. Love that mouse..
I'm using a MOTU connected via firewire and having no issues either. RME is known for high-quality drivers too, so it's unlikely that it could be drivers unless they are installed incorrectly.
What I suspect is that you've got some sort of a systems issue - possibly background processes that are eating up protected high-priority CPU time. A mouse tends to exacerbate issues with high priority processes if they are overrunning their expected time, which I believe might be your case.
I'd suggest as a start to take a look at the "DPC latency checker application". If there's an issue with latency, this application will indicate it. A more advanced application is "LatencyMon", which can also indicate which process are offennding - but it is a bit more technical for some.
A google search on the above terms will give you places where you can find out more information about these applications and where to download them.
It's a start...