You should post on the illumos zfs-discuss mailing list. The most amount of experts will be there to provide comments. I just saw the hostname of the machine; your "clout" may get you some attention. :-)

You very well may have some flaky hardware which is causing the issue, in which case, it probably needs to be fixed sooner than later. And maybe with some magic, you can get the pool into a happy state without rebuilding.