FH1100 Pilot says:
As someone who actually has had a complete loss-of-thrust t/r failure at an IGE hover in a Bell 206 I can speak to this issue from a practical standpoint not theoretical. Once the anti-torque is gone, the yaw rate builds up blindingly fast.
Well, I've never had LTE or a TR failure, so take this with a grain of salt, but:
When I was first instructing, we had another CFI who had an LTE on top of a mountain and crashed the R22 he was flying. A few weeks later I flew with him and he demonstrated a very fast rotation (still probably not as fast as if you have a TR failure but still pretty damn fast). He pointed out that if you don't try to look at individual items out the windshield, but instead treat the trees/houses/whatever as a blur representing the horizon, you can at least maintain a level attitude for a short time.
I find that most people who have never seen this demonstrated tend to drop a wing or the nose and start doing a pirouette, the danger being that not only are you spinning, you are now starting to translate so you are even more likely to tip the machine over upon landing.
Oh, and someone mentioned LTE vs TR failure. My feeling is that if torque is spinning me, I don't have time to diagnose the cause. I'm gonna get rid of the torque and put it down and we can figure that stuff out later. Not sure why LTE would be any less serious than a mechanical failure. (Yeah, maybe you could have prevented it, but once it happens seems like it's just as deadly). Not sure whether you'll get the same rotation rates out of LTE vs TR fail. Hoping not to find out!
We practice this stuff, but I have no illusions that a real life TR failure will be as benign as when we practice.
I have to say, though, that I have a strong preference for machines with throttle(s) on the collective because of this.