My guild is at the point where we have killed Staghelm, so the option of all of our available trinkets is now open to us. Originally, I was contemplating taking Eye and Necromatic Focus (stacking the mastery by simply applying DoTs).
However, I've been doing a little bit of research into the trinket Jaws of Defeat. What I read, though it was little, suggests that this trinket not only stacks from the number of spells you cast, but also from the number of targets that spell affects.
From Wowhead poster Bellabel :
"Holy priest, COH gives 6 stacks (glyphed.) This heroic version would give an instance -725 mana cost to all spells in one COH global. Toss a POH and bam, -1250 mana cost per spell in approx. 3 secs. Giving you 17 secs of mana savings!
Disc priest two POH cast and your in the zone. Just by looking at cast patterns, I can easy save 8k per cd. Is this trinket uber, it's so so for priest. Something like 20k mana in savings is easily attainable.
As it stands I've healed two 25 man hardmodes and my mana just manages to make it ....just barely. In tier 11 gear getting this trinket may give me a bit more wiggle room."
I was wondering if any priests on these forums could confirm this as fact. I am not saying that the poster of this information is lying, but I would prefer confirmation from more than one source. Thank you.