so im trying this on 12+
the damage of this ability is so varied, it’s wild
sometimes it does 0 damage (on me not on bubbled paladin), sometimes 7.5, sometimes 7
accounting for -40% damage reduction all the times i have different amount of health left (from same 100% 6.8 mil hp)
the question is, how can i get, reliably, 0 damage done (had it a couple of times) 
?
Have you been playing with a prot warrior when you took 0 damage? If yes, there might be the answer for you.
when that happened no
i completed it yesterday (paladin tank), got retch 3 times on me, one time got 0 damage, 20% and 40% health left after the other 2
20% hp left with no cds cause got none left, other time i got 1 shooted with no cd’s
anyway, back to the question when i finish the 12 tour and NW 13+ comes back lol
I can confirm this inconsistent behavior. The shammy in my group sometimes gets almost no damage, and sometimes he gets 1 shot through a defensive.