Mark on Death and Reflect (weird interaction)

I have found a weird interaction in t17 maps, when running both mark of death and elemental reflect mod,

I have 100% reduced elementa reflected damage taken, and I am suddenly get instant oneshot once mark of death is applied.

Adding more reduced elemenental reflect (through passive) tree solves the issue, but this weird interaction sounds like a bug. Why does mark of death increase ele reflect taken and overrides 100% reduce cap %?

Reduced reflect is additive with all sources of increased damage taken. If you have 100% reduced reflect and get shocked for 10% you would need 110% reduced reflected damage taken to still be reflect immune

Marked for death causing you to take increased damage is consistent with this.