You’ll more than likely get a lot of different opinions on this. I think (could be wrong) that ML is calculated on kill for regular monsters and EPs, meaning you can swap before the killing blow is deal.
Whereas with well monsters, ML on the main drop (the actual items that you dropped into the well) is calculated when the item is first dropped in. All side drops are, however are affected by ML on kill.
There are theories on drops being negatively affected by gear-swapping, towning, or even using skills/kiling the EPs too quickly.
Curious to see the input here as I haven’t seen a topic about this in some time.
well for instance if someone was to get an overspawn drop from an ep when first engaging with no ml but on swap they do have some ml..... that answers part of the question, perhaps some people have tested this with wells too.... perhaps dropping the main and then swapping to ml gear for the last hit.... would be nice to know for those of us exploring, sure MQing could be an extra handful of hours while keeping ML gear on 24/7 but at least you could make an educated decision on whether or not to swap or not and to your point, when it would be beneficial or detrimental