I jumped to a conclusion without enough time using the trinket.
I used it in early BT last week when I first got it. On Naj'entus I believe it fell off every time he bubbled - we were waaaay too slow breaking his shield. On Supremus it would fall of during the kite phase when I had to avoid a fire or something. On Akama I tank a side and we don't DPS the sides anymore, so I didn't wear any threat trinkets. On Gorefiend for whatever reason the warrior tanked - but that would be (I believe) an ideal fight for it. I tank Phase1 ROS, so I don't wear threat trinkets. Bloodboil was a pretty good fight for it. After the trash to Mother Shahraz I didn't wear it again.
There was another thread on Threat Trinkets I read somewhere here a few months back which was pretty good. Nowadays I generally use Icon of the Silver Cresent and Figurine - Crimson Serpent, and I guess I'm looking at replacing the Figurine with the Crusade card, and one day soon the Icon with the Hex Shrunken Head.
I know the original post mentioned Timbals Focusing Crystal. I had and used it for a while. The Spelldamage portion of it is nice, but the proc does little for you. I believe it's a 10% chance to proc on a 15s internal cooldown. Added to that is the fact that it's shadow damage, and the proc does very little to create additional threat. I think the Icon beats it pretty easily. However since you ask to compare the Talisman and the Crystal, I'd probably suggest the Talisman for single target threat.
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http://www.wowarmory.com/character-sheet.xml?r=Zul%27jin&n=Vanarina