Isn't just DISM (I'm not sure that particular one has been an issue for me) it is just one of a number of processes that can kick in - never have anything like that in Windows 7, etc. if you watch his video he does a clean install on all 3 devices and the only software he installed was to benchmark and those issues were occurring.
Posted my comments on there as Rroff2 - last I looked there were over 3K comments on the video so if the sort order is different it will be hard to find mine - I just tried from private browsing and couldn't find them :s