Anyone else running into this. Hit Rath several times and never stunned him.
It only stuns after you use the En Fuego ultimate. If it isn’t stunning even after that then you either missed the hit or it’s a bug of some sort.
As loko said, it’s only when En fuego is up that it stuns. for me it works, i’ve stunned 4 players at the same time with it, so i think it works (this was on PC)