Like everything else, that depends on the candidate. A person who has had 10 1-year jobs may have tons of applicable experience and be a better developer than the Loyal Schlub who spent two or three 3-4 year stints doing CRUD (or even proprietary trader front-end) app X. Given the rest of your post, I suspect the issue here isn't that you've had trouble finding good candidates with "10/1" resumes; it's that you simply are selecting them out due to bias.
"2) Its harder to find senior developers, regardless of what you pay. As Joel once said the good developers always have jobs, hence his internship program."
This actually supports the sentiment I expressed in response to your first point. It seems you're looking for an extremely specific and narrow type of resume--one that fits a particular format consisting of long-term, stable employment. You have a bias against other kinds of employees.
"3) the hire bar is, umm..., higher for senior developers as they are expected to do more, mentor, design architecture, etc. This means I'm more picky as to who I hire."
I have yet to see any interview capable of determining whether a person at the level you're talking about is actually capable of delivering on what you require. This last point is something that can only be adequately gauged in the context of your company's business by actually having the person work there, or work on a project there for some time. Companies are different. A person's ability to "be senior" in the way you describe at one company may not translate well, or at all, to another company.
I'm not trying to pick on you or be aggressive. I'm just commenting on a larger narrative--hiring practices in technology just aren't very good. It's not due to any deficiency in intelligence or honesty, either (most of the time, at least, I think). It's just that it's a really hard problem for which there isn't any one good answer.