I found this while doing a search for something else, but I think I can help. My vote is for ball joints. The guys doing alignments are used to newer cars and seldom check for balljoint wear unless they can't align the car at all.
Bad joints give the wandering sensation, and they also will cause tire wear at the very inside edge of the tire, that's difficult to see unless you turn the steering wheel a lot to examine the tires.
I've had to do the ball joints on two of my cars recently for just these symptoms.
Just my opinion, but it's fairly easy and inexpensive to remove the lower control arms and have a machine shop remove the big rivets holding in the balljoints, vs. doing it yourself. I was charged $12 per arm for removing the rivets, which is a lot let hassle that doing the drilling yourself.
