I agree very much with this point. From my perspective, the other sharp difference between these two is that there is much more nuance to the use of roxa, pending approval, than there is for an anti-viral. It's much easier to approximate ENTA's market with a "X HCV patients x Y% penetrance x $Z cost = revenue" formula than it is roxa's.
I still see a large market for roxa and am happy to average in. But risks, as you note, should not be understated.