Personally, I'm a lover of crit and mastery. I find that at the moment I have WAY more haste via gear than I feel I need, and spirit is a non-issue because I get my mana regen from intel procs. I just don't really feel that I need to prioritize spirit.
I may find myself using Windward Heart and Heroic Necromantic Focus (if the stupid thing will ever drop for me -.-) It might seem like a weird choice, but I smite heal, and the buff is more than easy to keep up if you HF on cd, and I tend to even throw up a sw on movement/low healing phases. I feel as if the steady intel/mastery is a prettier choice than a random and unreliable stat proc, and I don't like the intel loss/spirit itemization on Heart of the Unliving.
You are absolutely right, jaws is a very strong trinket. It's just hard to figure out an mp5 figure to assign to it.
If I had heroic jaws I might keep it for my holy spec. But, I don't.
You need some way to decide how much mp5 jaws nets you per fight. Then you need to guess how much extra healing you can get with that mp5.
From a muscle standpoint, the Seal is by far highest throughput trinket - especially if proc timings work well for the fight. The proc alone should land in the 4-7% range on a fight with favorable timings. Jaws shouldn't really come anywhere near that. It's an effic/burst tradeoff, once again.
Jaws: if you reach 10 stacks every time it's used, you save enough mana to cast 1 more PoH. 7 minute fight, ~5 PoH.
Seal: Each time it procs you have enough haste to get 2 extra PoH during the proc. 7 minute fight, ~10 PoH.
If you have mana to spare, the Jaws isn't getting you much. If you're OOMing, or if its procs time poorly, the seal doesn't get you much.
Trinkets like EoBP or WH are pretty constant.