[swelt]

Tank trinket: Purified Onyxia Blood Talisman - Item - World of Warcraft
DPS Neck: Sparkling Onyxia Tooth Pendant - Item - World of Warcraft
(+Caster Ring: Polished Dragonslayer's Signet - Item - World of Warcraft )

You can only complete the quest once, you can only select one reward (faction switch hax notwithstanding), you get the same quest & reward whether you chopped off her head with 9 or 24 friends.

So far I have been so underwhelmed by the rewards that I've been passing to others for whom it's a clear and obvious upgrade.

The tank trinket is unusual at best. I find it hard to imagine myself ever choosing to equip it. Am I missing something?

The neck looks quite nicely itemised for agility based physical dps classes, and might be a smarter choice for some tanks as an offspec dps item?

[Synapse]

You aren't missing anything. The tank trinket really does little to any but defense-starved tanks, who shouldn't be tanking onyxia anyway.

[Glittersmith]

The trinket is very useful for block sets though. Which is good for tanking Anub hard adds with.

[Theotherone]

I had the Head ninja'd from me the other day; wasn't too upset since I dont' see it as a great tank trinket anyway. However, it seems that the ninja-ing is getting worse and worse as the gear gets better. Some people really have no sense of honor.

[Maèl]

Rings and necklaces are a dime a dozen while trinkets are rare.
That's why I took the trinket although I was confused by it.

There's a new set of craftable resist gear for IC and you never
know when a big chunk of def and parry in one slot comes handy.

[Synapse]

Makes sense, Mael. That trinket is definitely a resist set boon.

[orcstar]

Source: Synapse You aren't missing anything. The tank trinket really does little to any but defense-starved tanks, who shouldn't be tanking onyxia anyway.

Trinket with highest avoidance in game?

[Norik]

I won the head on my very first 25man run. After looking at the trinket I came to the conclusion that I wasnt really impressed with it and gave it to my wife as the DPS caster award would be a huge upgrade for her.(And when the wife is happy, everyone is happy)
After a bit more time to think about it, I have added it to my "Will go for next time it comes up" list.

[Synapse]

In parry?
Against, oh, Gormok?
For as long as avoidance is being advocated as something in low priority, it's no big thing.

[Maèl]

There are not too many trinkets sporting def.

[Synapse]

Thus me saying it's mostly defense-starved tank thing over much else.

[Eravian]

It's usefulness (or lack thereof) will be more apparent once Icecrown comes out, I'm guessing. Who knows what fights will require you to swap in resist gear that may have lower defense values... maybe I'll get to bust out the Icebane gear that I don't even use on Sapph anymore again...

...although that would make me a little sad. Either way, the point is Resistance and a healthy amount of defense may come in handy in specific fights (particularly against something like... Sindragosa? Is that the big skeleton dragon that they show with Arthas all the time? I forget...)

[Mert]

While I wouldn't prioritise getting it first I do recommend picking up the tanking trinket at some point for the simply reason that Icecrown Citadel looks very likely to have at least one Magic Resistence fight (there's patterns for Nature Resist gear on the PTR) and, for a tank, it can often be difficult to keep the defense minimum in resist gear without giving up too much in the way of Stamina.

Since a lot of folk have kept their Repelling Charge to swap in for Hodir when tanking him in Frost Resist gear, the Onyxia trinket would be a natural upgrade for when you're in your new, shiny resist stuff.

EDIT: I guess that's what I get for leaving the thread open for ages before replying... my bad, I see others have beaten me to it.

[Durandro]

Source: orcstar Trinket with highest avoidance in game?

I thought so as well, that's alot of Parry. And the small amount of health regeneration could possibly save your life.

Maybe not the best trinket around, but not a terrible one. Especially considering how hard it can be to get the 'right' one sometimes.

[Maèl]

...and I'd at least try to stay well over 50% passive avoid while in resist/hp gear.
Though if it is better to gem def or uses this trinket comes down to what other stuff you have you can use. But you never have too many options.

Plus that DPS neck doesn't do it for me either. I've seen quite a few of those while the trinket is quite unique(and a bit weird).

[Eravian]

Weird trinkets generally serve a specific purpose, especially when they drop off bosses... although it's also possible (and likely) that it's itemized the way it is because that's what the old one was like, and now it's just been updated.

[Durandro]

Yeah, most of her drops are updated copies of the old drops. Classic had plenty of odd itemisation choices - such as practically everything having Spirit on it, and the best weapons had procs on them but no stats

Still, could be useful. I'd not complain if I got it..

[swelt]

The resist set thing is a good point, and probably the right thing to do will be to pick one up in a few weeks after those that will actually use the ring/neck in their primary sets have gotten theirs, and from 10 man where there's less people to compete with.

[drae]

The trinket is also great for heroic 25m Anub Add tanking. It's a ton of defense.

[Jadage]

Last night I won the onyxia head and promptly got the tanking trinket to replace eitrigg's oath. I read this thread saying that this trinket has the highest avoidance of a trinket in game, and, I thought it did when I looked at the stats. However, when I replaced my eitrigg's oath (normal version) I found that I lost .06% total avoidance. 114 dodge > 108 parry and 69 def? I'm confused.