Over the course of the last few Hodir 25 man attempts that hit the enrage timer (8 minutes I believe) I gained over 9,000 mana from Soul of the Dead (approximately 20% holy crit).
Thats pretty close to 100mp5, which is intense. In addition to the +crit rating, I can't imagine replacing this trinket with anything else at this point.
I did a little research this morning and well 1 thing i know for sure, Soul of the Dead will stay b/c the Crit is awesome and the mana back from it as mentioned above is just too good. As for the second trinket Spark of Hope will replace Spirit World Glass b/c Spirit World Glass gave me only an additional 100mp5 for 20 secs when activated. Spark of Hope on the other hand is worth a conservative 100 Mp5 due to the amount of mana you save on each spellcast plus you get an additional 15 spirit than Spirit World Glass. The other good thing is both effects are on equip.
I just got spark of hope last night and it along with the glyph of flash heal + Soul of the Dead is so much better on my mana.