I believe I have the answer to that one.
We currently have a support case running with McAfee about this. If the McAfee Validation Trust Protection Service is running because of one or more McAfee products are installed then you should see a performance degradation that is quite severe.
Without any McAfee product installed we tried copying a file of 3,5 gig to our 2012 server. That took 14 seconds.
Once we installed McAfee antivirus we noticed that the copy took 60 seconds.
With HIPS installed it increased to 90 seconds.
After that we disabled all the McAfee services we could, which left out the McAfee Validation Trust Protection Service. Started the copy and still 90 seconds. As I'm writing this, we (me and my colleagues) are trying to convince McAfee that there must be a bug in this service.
If anyone agrees with my observations please let me know.
We don't see quite the same performance degradation on Windows Server 2008 R2 SP1, but it is there. And it doesn't look good on Windows 7 SP1 as well.
We did the test with McAfee Antivirus 8.8 patch 3 and HIPS 8 patch 3 installed.