I know there is a 14 page thread on healing trinkets; however, it hurts my brain trying to transpose an opinion from a shammy, druid or pally into a priest theory, so I'd like to get a more focused discussion on trinkets specifically from Holy Priest perspective.

I'm finally almost epiced out, just need a few more badges for my Bishops Cloak, and I have yet to see prince or maiden drop a shard or justice. Other than that its my trinkets that I'm now turning to figure out whats best to keep in my bag.

Currently I carry the Bangle of Endless Blessings, Aussies Light Channeler, Lower City Prayerbook, Eye of Gruul. Most of the time I keep the Prayerbook equiped and trade of between EoG and ALC as they both seem about the same in the long run in terms of mp5 return, but I do like the fact that the EoG effect is passive.

On trash and a lot of Boss fights I have Lower City Prayerbook and Scarab equipped because they provide the most +heal.

However, for mana intensive bosses I find Alchemist's Stone and the Bangle to be irreplaceable. I use the Bangle in combination with Inner Focus early on when I know I am not going to be casting, i.e. Boss Transitions, Silenced etc. Later on in the fight I have a macro for whispering a feral druid for innervate. The combination of innervate and Bangles usually gives me over 7k mana.

See the 'similar threads' at the bottom of this page?

Holy Priest Theorycrafting
Holy Priest usage in raids

Also...
Healing Trinket Selection