Why not go pure health?
on lich sure it makes sense to go threshold stacking.
But take for example a character who has 2k life vs 4k life, baseline the 2k life guy has 400 treshold, and the 4k guy 800, 1000 threshold puts the 2klife guy at1400. that means he takes 600 damage at full, and 1400 at 40%(60% endurance) that means the 2k life guy can take 4100 in a singular hit(600 + 1400/0.4 = 4100) the 4k life guy takes 3200 damage at face value, then 800 at 40%,(3200 + 800/0.4 = 5200
Tldr, in pretty much every case, replacing those affixes with added health provided a better bang for your buck. Especially because they scale with %health which you want to be building as well.
Basically if a t7 endurance treshold gives you 200 endurance threshold, and the t7 flat health gives you 180 health, the 180 health translates to 180 health, and 36 threshold anyways.