I was unable to reproduce it. The CPU usage has been below 0,02% for ekrn.exe and 1,4% for mbam.exe if no on-demand scan was running.
If the issue has started to manifest just recently, it might have been cause by an update of ESET, ESET's module, MBAM, MBAM's module or operating system itself. Moreover, other applications might have influenced it as well.
Please find out disabling which of the protection modules resolves the issue. A complete memory dump from time when the issue is manifesting might shed more light.
Nevertheless, bear in mind running multiple security solutions at a time may lead to clashes. Even if it seems that two AVs run alright together, nobody will ever be able to guarantee that it will stay like that forever or that the 2 protections won't clash or cancel out each other when actual malware is encountered.
I am very satisfied with ESET today. But I think they could add a sandbox so the user could execute suspicious files without the possibility of infecting the computer. Another thing is please do not do anything that would compromise the system's disengagement as other famous brands did. I really like ESET because of its good detection and low impact on the system.