I think you need a Mirror Master achievement, or Champion of the Broken Mirror achievement. I do not remember for sure. Basically - you need to win TBM and you get flagged for immunity to those debuffs.
#1 thing to know is merc are not affect by this. So bring healers There is 2 opinions on this One is do the 4 missions that reward you with a collectable. Do each one 6 times. Fate Rewards the Bold, We make Our Own Rewards, In Defense of Health and Laxvanom Labors. And click the little things The other is Finish all content: Champion/Paragon. So, do all of the partisan, mercenary, and hero tasks. I think the second one is wrong cause I do not have all the Hero tasks done and either I do not get the debuff or it is so little now at my level that it is not noticeable. My healer merc handled this fine at lower level.
I may be thinking of something else, but don't those TBM debuffs cause merc healers to constantly try and heal you to full?
When TBM was first released (or maybe only during Beta), yes, the merc healers constantly tried to heal. But that didn't last too long.