I've been testing against my defense on the arena, and it seems that if the dog is the only one on the team, no allies will be cleansed from his passive. But if there is at least one of the twins with the discouri passive then all allies will be cleansed when the dog takes damage. Seems weird that there needs to be at least one allie with the discouri passive in order for the passive to be applied to the rest of allies. I will try to attach 2 videos to prove my point.
https://www.youtube.com/watch?v=GRvqPidknUM&feature=youtu.be