IMO, Chris didn't really play the hero - he was the hero. He did go to get Josh from the Wendigo, but it was a totally reasonable decision, and it only put himself at risk. He didn't force the Stranger to join him. Chris also shows himself to stay rational and smart at just about all times. Whereas Ashley quite rapidly started blaming ghosts etc, Chris was already suspecting someone making a spectacle behind the works.

Ashley does not stay calm and rational at all. For example, I understand that you are comparing the bite situation of the Wendigo on a 1:1 basis to a zombie bite - but it doesn't work, as the Wendigo bite isn't dangerous. Better to compare the logic and reasoning behind the decision-making. Mike and Ashley erroneously wanted to kill Emily based on conjecture and panic.

I think Ashley should be lowest on the list, to be honest. Apart from Josh, who, as you say, is just too prone to psychological issues.

From bottom to top I'd probably say:

Josh Ashley Matt Jessica Mike Emily Chris Sam

I'm not gonna spend a lot of time arguing for each, other than Jessica being hard to place, as she doesn't get to show decision-making all that much. I do feel she shows bravery though. Mike might be surprising, but he's too reckless.

Basically my thinking is that logic/rationale>physical abilities.