Nihilus doesn't take any damage on Phase 4 of the Heroic Sith Triumvirate Raid

Hi all, as promised, I looked more into the interaction between Phase 4 Darth Nihilus and Nightsister teams (Mother Talzin Zeta) and here are my findings:

Things to take into account:

• Darth Nihilus ability in Phase 4 of the Sith raid: "Lord of Hunger" which states: "At the start of his turn, Nihilus recovers 3% Protection for each buffed enemy. In addition, whenever an enemy damages Nihilus with a Basic ability, he inflicts Defense Down on them for 1 turn. If they already have Defense Down, they lose 25% Protection and Nihilus gains that much Max Protection (these effects can't be Resisted)."
• Old Daka basic ability "Insightful Blow": "Deal Physical damage to target enemy with a 75% chance to Stun them for 1 turn. Deal Physical damage to a random enemy with a 55% chance to Stun them for 1 turn."
• Mother Talzin basic ability "Ichor Lightning": "Deal Special damage to target enemy and, if they are Plagued, inflict Plague for 3 turns. Deal Special damage to all Plagued enemies which can't be Countered."

What causes Darth Nihilus to stack up a very large amount of Max Protection. Main factors are:

Old Daka using her basic on Darth Nihilus:

• If Old Daka has Defense Down and both times she deals damage with her basic land on Nihilus it results in Nihilus gaining 50% of Old Daka's Max Protection being added to his own Max Protection. So let's say Old Daka has 20.000 Max Protection, if the previously mentioned scenario occurs, Nihilus gets 10.000 added to his own Max Protection -> Working as intended.

Mother Talzin using her basic:

• If Darth Nihilus has Plague and Mother Talzin has Defense Down, when using her basic ability, she will deal Special Damage 2 times (once from the ability and another Special damage from Plague). This will result in the same Max Protection recovery for Nihilus as mentioned above for Old Daka. -> Working as intended.
• If Darth Nihilus has Plague and Mother Talzin has Defense Down but uses her basic on Sion or on the minions, Darth Nihilus will still receive Special Damage for being Plagued, and will still gain 25% Max Protection.

In regards to this part that @NoHalfsies mentioned:

"-If Nihilus has multiple stacks of the plague debuff, his protection drain is triggered on a basic attack from MT even when she doesn’t have the defense down debuff."  

If Mother Talzin doesn't have Defense Down but Nihilus has Plague, the following occurs: Talzin deals Special damage, gains Defense Down, then deals Special Damage to all Plagued enemies which results in Nihilus gaining 25% Max Protection because the damage comes from a character which has Defense Down and uses a basic ability. It has to do with the order of operations. -> Working as intended.

Only by taking into account the two scenarios mentioned above, it explains how at the end of a long Nightsister run in Phase 4 a player can no longer get through Nihilus's Protection when he is close to Enrage. 

Hope this helps.