I really don't think the comparison translates, because Amaker's main problem was an inability to bring in talent. I think as a whole RR brings in and will continue to bring in talent (outside of the short term lack of talent on defense).
I have heard several people say that getting rid of RR will set the program back 5 years, and while I don't agree that RR should be fired at this juncture, he should definitely get a 3rd year. But at what point does this become a situation that just doesn't fit, and instead of spinning the wheels for another 2 or 3 years do you cut bait and start over. And saying that turnarounds can't happen in 2 years is simply incorrect. Saban at Alabama, Meyer at Florida, even Tressel at O$U. Remember that OSU team went 6-6 in 1999 and 9-4 in 2000. They then went 7-5 in his first year with a huge "lack of talent". I think next year is huge for RR, this team has to finish strong and go to a new years day bowl, otherwise its time to consider the possibility that RR might not be the right fit.