I've noticed Riot Strike is not only supposed to interrupt an ability, but prevent that ability being used for the next 4 second.
I don't know whether it's a glitch or it just doesn't work but I'm constantly fighting healers when I Riot Strike their heals, and immediately after that they cast it again.
There is no 4 second delay, and it's aggravating because it makes fighting healers impossible to do alone. They just sit there and keep healing themselves.