Untalent Gift of the Eaerthmother and spam Rejuv on purple phases, if you want to be even remotely useful on this encounter. Also, Nature's Ward Rejuv proc doesn't create a stack of Deep Corruption so you might as well talent that.

We tested Moonkins casting rejuv (and refreshing before it fell) on people with Deep Corruption on trash and it still put a stack. So as far as I can understand there's no reason to spec out of GotEM.

I spent a whole night healing my group with rejuv giving zero stacks. Test on bosses, not on trash.

Can anyone confirm this?

Also, a side question: why would you spec nature's ward if rejuvenation was already not causing a stack?

I just saw your spec, makes sense.

We don't really have the option to ditch druids. Can you elaborate a bit on why were are sucking on that fight in particular? Seemed like finding out about the gotem thing would bump us up a bit for purple.

Backing Kluian's findings: as a Moonkin, my Rejuvs were giving 1 stack per application. This result is from the boss too - not the trash.

Now I'm just flat out curious about how to replicate the bug Torty experienced...

Because we don't have raid cooldown for any of the purple phases, we don't have tank cooldown and aoe healing can be done by holy paladins so that's not a problem. Using my guild's tactic, we had 4 purple phases out of 6 possible combos and there are 7 ooze phases on the encounter. I think we've got 5 purple phases on the kill. One class being almost useless on 5 phases out of 7 - you can do the math.
3 resto druids, 26 wipes. That was the whole tactic on purple phase we were working around.

World of Logs - Real Time Raid Analysis
You can dig the log if you want.

P.S. Stop testing stuff on trash, in dps spec, without clear rules like 'only you healing the group'. It's not testing, it's what makes testing bad.

Check each individual explosion before you jump into conclusion. I couldn't find any Rejuv application that caused explosion. There are some strange explosions that didn't have either a heal landing or buff applying 2 seconds before the explosions from any of the healers, but no 'X gains Rejuvenation from Torty/Yach/Noldorimbor' and explosion following that in the first 20 wipes at least.

Wipe #6 World of Logs - Real Time Raid Analysis
[21:21:46.563] Soraya Tranquility Kym +9045
[21:21:46.631] Kym Deep Corruption Kagemoth 50256 (A: 8431, R: 18340)

Wipe #15 World of Logs - Real Time Raid Analysis
[22:46:02.775] Y�*ch Tranquility Zenevieva +12809
[22:46:04.486] Y�*ch Tranquility Zenevieva +12808
[22:46:06.305] Zenevieva Deep Corruption Roguishh 24915 (O: 2983, R: 37198)

The only one that I found looking suspicious:

Wipe #19 World of Logs - Real Time Raid Analysis
[23:18:15.310] Kagemoth Prayer of Healing Sludgiez +8911
[23:18:16.948] Kagemoth Prayer of Healing Sludgiez +8739
[23:18:18.936] Kagemoth Prayer of Healing Sludgiez +8742
[23:18:20.165] YÃ*ch Wild Growth Sludgiez +1925
[23:18:20.517] Sludgiez gains Divine Aegis from Kagemoth (Remaining: 11698) (This one I'm pretty lost. There's no heal, but only a Divine Aegis application.)
[23:18:27.799] Sludgiez gains Rejuvenation from Torty
[23:18:29.294] Yor'sahj the Unsleeping's Deep Corruption fades from Sludgiez
[23:18:29.796] Torty Rejuvenation Sludgiez +5334

So we can see Rejuv application roughly 1.5 second BEFORE explosion and a hot tick 0.5 seconds AFTER the explosion. I can't explain that as I can't explain some other explosion that happened with no apparent heal/absorb landing 2 seconds before the explosion (see wipe #15).

It might be that a first rejuv tick applies a buff if you don't have GotEM talented, and that might be the reason why neither of us 3 noticed Deep Corruption getting a stack from Rejuv. If anyone has Yorsahj not killed yet and feels like testing, please do that. I will try to fraps next week if I get a chance to heal, but that's obviously Wednesday-Thursday at best.

Essence of Dreams (the green buff on Ultraxion) isn't benefiting from something from our healing and I cannot work out what. From my own and other logs I'm browsing on WoL we tend to get around 44%~ of our total healing done while having the green buff up while Shamans and Holy Priests get 52%~.

Example logs where the time frame is only after having the green buff, and being dated after the most recent change to the green buff:
2x Shaman - 53%
Holy Priest 50% & Disc Priest - 40%
Paladin 41% & Druid - 44%

It doesn't seem to be a matter of overhealing as we seem to have among the lowest % overhealing done by Essence of Life while other classes get around double that. I'm somewhat puzzled how we are aligned better with Holy Paladins and Disc Priests(!) in regards to this buff instead of Holy Priests and Shamans.

If the December 2 hotfix is still intact, it'd easily explain your findings:
Thus it no longer triggers from most Wild Growth ticks + low stacked Lifeblooms.

There's also a bug where Wild Growth won't be applied to full HP targets.