I like your take on this. Building high expectations of a smack-down are unwise, and set up Ryan for either trying to hard, or seeming to underperform if he doesn’t. Biden can perform better than his public perception, and is somewhat dangerous.
A Vice-Presidential running mate is always a potential millstone. Ryan doesn’t have to hit a home run, but to appear credible and avoid stepping on mines. He needs to seem mature, alert, competent, and in command of the facts. I do not know Ryan’s style, but Biden seems the perfect mark for rope-a-dope: manipulate Biden into a rambling defense of the Obama record and he will beat himself senseless.
I agree. It's a difficult situation and Ryan has to avoid being trivialized, on the one hand, or being turned into a cruel grampa-destroying meanie, on the other.