so, I'm obviously going for Heart of Unliving - that's the easy part. But I'm puzzling about the second trinket slot and would like to hear your take on it. Which do you think is better for holy priests,
Oh, maybe I should mention that I'm healing a 25man raid, hence the emphasis on mastery over haste. Haste is at 17-20% with raid buffs, that's plenty, and there's a lot of gear with haste on it this tier as it is.
It never occured to me to actually check the AMOUNT of the flat intellect on the trinkets (d'oh - but I assumed that since they're the same item level, it must be the same too). That is one heck of a difference. I have to say, mana is a problem only on Madness of Deathwing, which we're still learning at this point, but even so Intellect is probably more beneficial than spirit.
The thing is, I like to have a trinket that gives some form of mana regen/saving, like the Jar and the Core in Tier 11, or my beloved Jaws of Defeat in Tier 12 (which is the reason why I healed heroic Baleroc as holy, and successfully, haha). But I might actually forego that this tier and see how I'll fare with Windward Heart and Seal of the Seven Signs.
Heart of the Unliving and Seal of the Seven Signs are both worth it, but I would say that you indicated you have the heroic jaws, which I did not have when I healed heroic Baleroc as holy, so only use the normal version or better. Heroic Jaws craps all over LFR versions. Here is why. It sounds like you are using "Elitist Jerks" standard stat weightings for holy, which is 12.5% haste and reforge mastery as the primary of the secondary stats. Some choose to go haste build especially on 10 mans. This is old news. The point is that your crit is still your lowest stat. The best time to use Windard would be when you have the crit buff from single target chakra. In a 25 man, holy priests are best suited to be raid healing (AOE Chakra most of the time). I'm assuming you are at first major haste threshold of 12.5%, haste still becomes a more consistant throughput stat than crit regardless. The exception of course is mastery, and mastery is really the only thing keeping us from stacking haste to begin with. Extra haste is not a bad thing when its on a proc for a multitude of different reasons. I hope this was at all helpful, again it really depends on in which situation you are using which trinket and why (which usually means they are doing a good job on trinkets). Fell free to message me if you want more information, but again those two choices are considered Best in Slot based purely on STAT WEIGHTS, not situational cirucumstance, as it was also pointed out Intellect right now is still the absolute top weighted throughput stat for obvious reasons (% based max mana pool regen ftw...for now).
I strongly disagree with Seal of the Seven Signs. It has proved to be incredibly underwhelming so far given that it is an exceptionally long ICD for this kind of trinket (I dropped it fairly quickly).
For progression, I would advocate Heroic Jaws and Heart of Unliving. If you have a surplus of mana, I would suggest you swap H Jaws out for Windward Heart. Even with low Crit, your raid heals should proc Windward Heart sufficiently that it would prove more useful than the long ICD Haste buff.