The DiskWarrior trick seems to have made the difference for me, although it didn't happen immediately. Over a few days I had, in no particular order, and often more times than once:
- Erased all files in /.fseventsd/ and restarted the computer
- Re-built the Spotlight index for the drive
- Repaired permissions
- Found some directories with ridiculous numbers of files in them (/private/var/tmp had over 20K files!) and deleted them.
- Rebuilt the directory with DW
It was only after #4 that #5 made the difference. Oddly, for a few backups I was still getting the high file count messages and hour-long backups:
Jan 18 07:16:38 <hostname> com.apple.backupd[8290]: Copied 90379 files (8.8 MB) from volume Macintosh HD.
Jan 18 07:50:40 <hostmane> com.apple.backupd[8290]: Copied 88790 files (364 KB) from volume Macintosh HD.
Until suddenly I saw this:
Jan 18 09:10:54 <hostname> com.apple.backupd[9569]: Copied 92034 files (41.0 MB) from volume Macintosh HD.
Jan 18 09:11:05 <hostname> com.apple.backupd[9569]: Copied 112 files (276 bytes) from volume Macintosh HD.
and since then the file counts have been in the hundreds or low thousands, and the backup is complete within a couple of minutes. Hooray!