In my opinion this is just a big trap for those with less experience. They just see the 30% and think "What? He'll die from the slightest bit of damage, no way he gets into the raid!". I think this moves away focus from the actual issues with fury and some refuse to play the spec over such a trivial thing. I mean the extra health and bloodthirst is factored in to make it work.
People are talking about unavoidable damage such as Nythendra and Ursoc, I've fought them plenty of times (as well as Elerethe, 3/7 so far) in mythic and I've had no issues whatsoever. Unavoidable damage isn't meant to kill you on its own and it wont kill you as fury either, the damage increase punishes you for making mistakes, taking avoidable damage. But in that case the mistake you made is the problem in the first place, not the damage debuff. I haven't had any issues in "deaths out of my control" on any of these bosses. So personally I think it's a thing most people take way to serious without realising that the difference is miniscule if so ever existing. However I can be wrong and I'd love to have a proper discussion on this and set the stone once and for all.