I think Yubikeys are great but I don't use them for anything related to bitcoin. As a second factor (something you have) with something you know they do a lot for security if used as they are designed.

I could be wrong but I am not aware of the company marketing them as useful in the way you describe. On top of that there are tons of people giving bad advise online. Sounds like you learned a lesson which really is worth the money spent. I've learned many lessons this way. Too many to name really.