I saw the chiropracter on Friday, and it was a wonderful experience. The woman I saw had a completely different diagnosis than any other person I've seen, and made more sense than anything else.
She thinks that everything stems from a bad ankle sprain I got 3 years ago, before I even started seriously running. From that, I have a weak ankle, which meant that as I stepped up my training, I tended to roll my ankle out, which put strain on my calf. That strain turned into calf pain. From that, I ended up with a chronic tightening of these little ligaments that run down the side of the leg. And when the quad muscle swells up with blood when I'm running, it puts lots of pressure on those tightened ligaments, which causes the burning soreness. Because of all that, I started favoring my left leg, which caused my pelvis to tilt and my spine to become unaligned at the bottom.
So, she is optimistic that with adjustments of the spine and pelvis and some specific stretching, I should get better :) She also said that we'll know if this is working in about 3 weeks. But, this diagnosis actually makes sense for where I hurt (my previous diagnosis, sciatica, is supposed to be down the back of the leg, which isn't what hurts for me). Also, it explains why the steroids didn't have any effect.
So far, I do think it feels a little better, and I'm feeling hopeful :D