Just a note, it was confirmed on 12/5 that this trinkets proc does not increase mana tide unfortunatly.
[Resto] Raiding 4.1 - updating for 4.3

EDIT: Derp. Guess I need to learn to patch notes.

What does everyone think of Foul Gift of the Demon Lord - Item - World of Warcraft

It has a very high uptime and gives about 8% harmony bonus(at least for me, 21% to 29% harmony for me)

Here is a link in an Ultraxion Kill World of Logs - Real Time Raid Analysis

Foul gift had a 59% uptime. It lasts 20s and it s god aweful obvious proc.

It's a decent trinket due to the low ICD as it works to an average of 500~ mastery passive.
However you must keep in mind you have to refresh your Harmony after the proc happens for it to actually benefit you which is a reasonable downside if you have to do this on more than an infrequent basis.

For what it's worth it is a 20sec duration and a following 25sec ICD which amounts to a 45%~ uptime. For some reason your log seems bugged by having double durations of the buff twice which is why the uptime seems so good for you there.

I am struggling to find a trinket with a better proc tho. The effect lasts 20s so a recast of HT/Nourish/Regrowth still gives you a good ~15s of the proc.

I am going with this as my preliminary BiS list Profiler - Wowhead

I plan on using a different spec tho, not sure why it won't load the other spec. 8/2/31 with moonglow maxed and 2/3 in furor, 1/3 in genesis

I personally believe that when starting heroics you should bump up your mana regen and then cut back as you feel comfortable with rather than running on fumes unnecessarily. I went from 1600->2300 Spirit and took the 2 set from LFR (I still had a 378 gloves so it averaged out as an equal ilvl/stats exchange) for now.

Depending on your tactic on Zon'ozz (1 camp or 2) it can be very mana intensive in both phases which should lean you towards more regen, I noticed issues on Yor'sahj heroic but that was without the Mana Void trick so that is a pending issue. Spine/Ultraxion seemed rough enough on normal to warrant higher regen too.. but obviously how your guild plays and your style of healing will impact this issue more for you personally than anyone else can guide you.

what is this "mana void trick" you speak of

I'm guessing saving a low HP mana void from an easy combo and killing it off when you get a harder one. That's what we did and it helped quite a lot.

Are you talking about 10 man or 25 man Zon'ozz here?
I'm off-spec healing in our 10m raid and also healed Zon'ozz 10HC a few days ago using a 8/2/31 mana spec with <1200 spirit, two int trinkets and 4t12. Mana is tight but I never felt I didn't have the mana to keep the raid alive in our attempts and our kill; without dying I could sustain ~29-30k HPS for the whole 6 minutes.
Thus I'm definitely keeping my low spirit setup until there's a fight where I really feel mana starved before the end of the fight.

25 and our tactic involved each bounce hitting the majority of the raid, rather than having half the bounces hit only one person or having the raid split in half and having people run out with the debuff.

Are you guys 2 healing or 3 healing (if 10man) for Zon'onzz? We were 3 healing it got it down in 5min 30 mana was tight at times but definitely had more to pump out at the end. H Ultraxion is a bit of a pain in the ass waitin for the blue crystal to come out resto's dont seem to be able to pump out as much as the other classes.

For those interested in [Windward Heart] , here are some logs of me using the 410 version of it.

World of Logs - Real Time Raid Analysis

World of Logs - Real Time Raid Analysis

Seems very powerful to me.

..Forgot to add that the spell is called "Nick of Time"