So after much frustration and seeing far too many Vials of the Sunwell destroy my hopes and dreams- Timbal's Focusing Crystal finally dropped for me last night. I haven't gotten a chance to test it in a raid setting yet, but I'm looking forward to it Tuesday.
...So my assortment of trinkets is now:
Hex Shrunken Head The best by far. I'll always have it equipped.
Darkmoon Card: Crusade Definitely a little bit better than Timbal's but only on fights where continual casting with no interruptions is guaranteed. I'll keep using this guy on Shade of Akama, Teron Gorefiend, and other similar fights.
Timbal's Focusing Crystal Just a notch under Crusade but without the effective "must not stop casting" restriction. A great passive general use boss fight trinket and one less thing to worry about on some of the more intricate boss fights. (Worrying about the Crusade buff dropping off is a minigame in itself!)
Icon of the Silver Crescent Not for boss fights, but better than Timbal's and Crusade for soloing, trash, 5-mans, etc. If you're going to have significant breaks in the action the cooldown on this trinket effectively shrinks. Plus this is just great fun on large trash pulls. Activate Hex, DoT everything, activate Icon, DoT some more. That's a lot of added damage when you have 40 seconds of ~+200 damage applied to all your DoTs on several targets.
Fetish of the Sand Reaver Gotta love how this trinket still kicks ass at level 70. It's my best buddy for AoE pulls, especially in Hyjal!
A nice little collection if I do say so myself. Now I can drop my prejudices and start running Magister's Terrace with Shadowpriests to help them get theirs. Yes, I was an evil bastard and wouldn't run Terrace with a Shadowpriest...but hey I'm more than willing to help them now that I have mine. =D