Yes I was wondering the same thing when I first started however he tooltip for ravage is wrong it is very much interruptable. Happens to me all the time by people who actually know what the hell they are doing instead of those that scream nerf cuz they suck and are unwilling to try and get better. I will post a screenshot tomorrow as proof.
Seriously, stop. An actual interrupt does not work on ravage. It requires some type of CC (stun, mez, kb, etc) or vanish to break it.