You include facts about the On Demand Scan. I should first ask "Is it running?" It should correctly bow to other running processes so I don't think this is the problem. The rest of this message assumes it isn't running and this isn't the problem.
The other item you might check is Script Scan. By default this is turned off on servers but if you had set this with an older policy it might be preserved. Turn it off for servers. That seems the most likely culprit.
The next thing you should do is to set the policies to "McAfee Default" for everything on the server. Use that as a starting point for diagnosing issues. Then download the McAfee Profiler from the knowledge center (kc.mcafee.com) and collect its output. It will shed light on the biggest cultprits using processing power. You can post some results here and some folks can offer suggestions on processes.
Moving to vse group as it's a closer match.