So I just noticed that my FB contacts are syncing again!
Between last time I checked and now, I did the following:
1. Followed
this fix at androidforums, which didn't seem to help immediately
2. Flashed netarchy-toastmod 3.7.5 kernel
3. Rebooted
Then I got a notification that said "Facebook authentication has failed," clicked on it, and was asked to enter my FB password. So I did, and lo and behold, my contacts are back.
I'm not exactly sure what fixed it. Either:
1. The androidforums fix worked, but only after a reboot
2. Flashing a new kernel fixed the problem
3. HTC just happened to fix the problem on their side at the same time I did all of this
Anyway, it's working for me now. Just thought I'd share.