On the other hand, as of this writing, I have 245 answers and 48 questions. I can't remember the last time I've seen a question asked by a 10k user other than me. Is my usage pattern unusual, and should I be concerned about it?
I can imagine a few reasons:
High reputation users have acquired a lot of knowledge—not only in a technical sense, but knowledge that helps them find an answer to their own problems more quickly. Writing good answers requires thorough research, and after contributing hundreds of answers you might be more efficient at solving your own problems, hence no need to ask questions anymore.
High reputation users know how the site works. They know they cannot ask a bad question that doesn't show research effort, because it would be downvoted or closed. Don't forget that high reputation users could be held to higher standards.
Writing up all the things you tried and what research you've done often helps you solve the issue on your own. How many times have you written up a question just to delete it again because you found the solution while typing and explaining your issue?
High reputation users ask their questions on other sites. I sometimes post my Apple-specific questions on Ask Different. Of course this does not mean that I don't trust our community to be able to answer them, but I sometimes like to find out how other communities "work", and I cannot spend the time answering on other sites—so I do that through questions.
Another motivation could also be that they are ashamed of asking on this site, because it could be seen as some kind of deficiency not to know something. But this is just speculation—a well asked question does not need to be hidden somewhere. It does not only help the asker, but all future visitors with the same issue.
Is my usage pattern unusual, and should I be concerned about it?
No, don't worry. As long as you provide good content we don't care if it's in the form of questions or answers.
A lot of the good, topical questions on SuperUser fall in or around the same areas of expertise, so if someone is making a lot of answers (and the answers are good/valid/upvoted/etc), chances are they simply don't have anything they need to ask that would be answerable and good quality and topical.
On the other hand, these users may have accounts elsewhere on the SE network where they primarily ask questions and post few answers. I'm that way on sites like StackOverflow and Mechanics and Pets, since I'm not as much of an expert in those fields, but the types of questions that I would ask on SuperUser, I'm already able to answer myself -- either by googling, doing a little research in technical manuals, or just know it off the top of my head.
On sites like StackOverflow the Q/A ratio could be more balanced for high-rep users, because the topic range of SO is much greater than anywhere else on the network; you may be an expert in C++ programming for GNU/Linux, but if you suddenly start on a project involving Ruby on Rails running on Windows, you might be chock full of "noob" questions that are topical for SO.
That kind of thing is less likely to happen to high-rep SU users because the site is more focused, unless, say, you already know tons and tons about Windows, but you're new to Linux, so you could ask your Linux-related questions here. But a lot of our advanced userbase tends to use both Windows and Linux quite a lot, so even that situation is somewhat of a niche.
You shouldn't worry. Some people just know that answers gain more rep. As an example, I only ask questions when I'm stumped. If I have time, I answer questions when I lurk around SU.
Your rep is just a number, and it's easier to earn by providing more information to the site (i.e. answers). So again, don't worry, you're normal. Well, as normal as normal 10k+ users can be... ;-)