You may already have seen this, but in case you haven’t, @modal has created a spreadsheet that can be used to calculate the probability of getting MIs with various affixes How to determine the drop chance for an MI w/ specific affixes
I sometimes use it to get an estimate of how long a farm it might be to get a given affix or affix combo.
The MIs in Lee’s build are single-rare, so not insanely hard to get, but it could still be quite a journey.