Wow, Brent - it sounds as if you're doing everything right. It would appear that your body just has a tougher time than most adjusting to elevations above 10K'. I'm definitely with Harvey on this one - I suspect you just need more time in that 10K'-12K' zone before trying to go higher. A few nights on Baldy before your Whitney trip would certainly help the cause.
My wife has a similar issue. I can't count the number of times she's gone from 1000 feet (Atlanta) to 10K' within 24 hours, and never once experienced a problem. However, the first time she went above 12K', AMS slapped her silly. We eventually found that if she sleeps 3-4 nights at/above 8K', she does OK at the higher elevations. She still has Diamox just in case, but the extended time at moderate elevation seems to have done the trick for her. It could be the same with you, only the need might be to spend more time in that 11-12K' range.
Hope you get it licked - AMS is no damn fun! My one and only experience with it was at about 13K' on the Whitney main trail a couple of years ago. Eventually I realized my problem was that I was sleeping at 3600 feet in Lone Pine. Didn't matter that I was dayhiking to 12K' each day prior to Whitney - my body was not truly acclimated because I was never really at rest for any length of time at elevation.
That one episode really confused me because - like so many other numbnuts out there - I thought I was "immune" to AMS since I had never had it. Upon reflection, though, it was apparent why I had done Thirteeners and Fourteeners in the past with no issue - they were all in the Rockies, where you can't avoid sleeping high. That sold me. Since then I've been careful to always sleep high (2-3 nights) before attempting higher elevations, and have experienced zero issues. I've never taken Diamox, but always have it in my pack in case history repeats. AMS can be debilitating, but your kryptonite line was right on target - once you've descended below a certain elevation it can quickly go away.
