I noindex and nofollow all media attachments and archives. Althoug a bug is possible, it is best practice to do this or you will risk having no many pages indexed with as you said, flimsy content. It will not sink a site (happened to me) but I cant see it as being good.
On the other hand, my UK site wasn’t set to noindex attachments and my pic of thunderstuck 2 ranked for thunderstruck for 3 days. It was nothing but one pic and a title…
go figure that one out LOL!