Our work security uses both MWB and Eset in the presumption Defender isnt impressing itself. I have over the past few months noticed (and had to intervene) if you have multiple threat systems 'alongside' one another then more management tactics are required to stop them overzealously scanning and slowing systems to a crawl.
You have smart scans, startup scans, rootkit scans whatever - you get the picture and if all these products are randomly doing what they think is whats needed you turn an end user machine into a windows ME machine eventually. I think having these technologies is great but not when it comes to either many false alarms or the users complaining all the time of their slow systems.