Very significant numbers, worth considering for flies. At the risk of sounding biased, I think it's safe to say the mortality levels on the high end are predominately due to gut hooking with bait. That's also where the circle hook has the most impact, because of it's tendency to slide out of the gullet and catch on the lip.
I know my mortality rate is no where near 1 in 10. I'd go as far as to say it's not 1 in 50, although long term affect on the fish is unseen after it swims away, I'd even wager one in 100 with regular barbless hooks. Even still the circle hook may have a place in flyfishing. I've tried pogie patterns, sand eels and crab patterns on circle hooks. The pogie patterns were aggravating because I wouldn't hook up - partially because of the way I fish them. Usually fast but always herky jerky and set right away. The sand eels would have fared better but I couldn't get the balance right with those odd shaped hooks.
The crab on the other hand was a perfect match. Stripers tend to swallow crab flies. It's rare for me to have a bunker or eel fly hooked deep, but with crab flies it's common. I believe they put them right on those crusher plates as soon as they swallow them to avoid getting pinched.
It's hard not to set the hook the way we're used to, but the circle crab is a good use for circle hooks in my opinion. Even still the hooks used for bait are not ideal for flies. It would help to have circle hook manufacturers pay attention to fly fishing hooks with the features of circle hooks.
Maybe that could be a project for the FORUM.