Harvey, or mrrabbit if you prefer, the guy at the LBS says he used a tension meter and was well within recommended tolerances. I'm going to ask what tension he thinks is recommended.
After reading everything I can find, including here and another bike site, I suspect it is a combination of issues. That wheel was way out of true a year or two ago--I can't remember the cause, but I think I had a fairly high speed blow out, but I didn't crash or anything. I used a spoke wrench on it and had a devil of a time getting it true. This was long before the 1st hub failed. However, I'm wondering if the rim is either warped or has some issue I can't see that causes the forces to be distributed unequally to the hub. That, plus 28 spokes, plus almost 200 pounds plus maybe some over tensioning to get the rim trued might combine to cause the problem.
In any event, I'm getting a new wheelset with 36 spokes and 3x lacing. My buddy at the LBS has never seen this issue before and he tells me he uses a tension meter when he rebuilds (ie, installs a new hub), so I'm going to give them another chance, but with brand new everything. If this one fails, I think I'll just give up and go buy a new bike!