There was a paper written some time ago when the DAAs were a concept but not yet a reality. Sorry I can't find the link to it but the gist was as follows:
Mathematicians got together with medical specialists studying the hepc virus and how it mutates to escape threat. They calculated that if the virus was disabled in 3 different places at the same time then there was no possibility for it to escape via mutation. ie. 3 drugs with different actions would be a guaranteed success in eradicating any virus that was exposed. To date I don't know if their theory has been disproved but the concept made sense to me. I don't know if ribavirin was counted as one of the 3 DAAs.