One problem with Windows Defender I believe is that if you were a malware author the first AV you'd want to try and bypass is Windows Defender as it's the default which is used on most Windows PCs for your 'MVP'.
Bypassing other AVs would really be a 'nice to have'
Malware authors have tooling to run their payloads across many vendors all at once. I'm sure Defender is on the shortlist, but it probably doesn't matter much.
Further, AV is inherently a "catches known threats" technology, as much as any AV may pretend otherwise. Some people will always get owned but by virtue of those users' AV picking up samples the sample will eventually make it to various AVs.
If your goal is to avoid AV bypasses, I'd suggest changing your goals. Instead, treat AV as it is - a technology for finding known bad things. If you want to avoid unknown bad things you need to take another approach.
The time where AV business was just catching signatures, is long gone.
ANYTHING that touches lsass.exe, no matter how, will trigger AV these days.
Go and try to compile your own customized version of Mimikatz, unless you are malware developer, you will not manage to get one that doesn't get flagged.
I'm aware of the fact that AVs are not just hashing binaries or whatever. I'm well aware of how AV works in general. My points all stand imo. AV is a reactive technology.
Bypassing other AVs would really be a 'nice to have'