Am I coiling it wrong? (a WHM OOM question)

[Lionsden]

I'll list down where my mana goes completely bonkers for each turn as below:
Turn 1) 3 Stacks and above, I am pretty much Cure II ing 80% of the way.
Turn 2) ADS at 50% and below, same reason above
Turn 4) Double Dread, Cure II 100% ;_;

As a WHM mana management, especially over sustained fights is always going to be an issue unless they change the way Shroud works and make it scale with gear. This being said, PIE should be your most important stat after MND. Mulled Tea (HQ if you can afford it) should be your go to food. You should look to pick up your AF2 pants also as it will give you a huge PIE boost. SS is great, I love it, I think it is more beneficial than most people give it credit for, that being said it is not as important to have SS over a larger PIE boost. PIE is currently our only scaling mana regen, and the larger the mana pool we have the longer we can sustain through a fight.

Now to address the issues you are having more specifically.

Turn 1 - You should be able to manage 1-2 stacks with just Cure, and the occasional Cure II. You should not be needing to use your healing cds during this phase. You should also not be dumping to much mana into healing before the split. Obviously, you want to keep your tank alive and people up, but if you enter the split with low mana already you'll usually end up with issues.

At 2 stacks I generally Virus, then Seal + Cure + Cure II + Cure + Cure II is generally enough to keep the tank up with no issues. (This may be different depending on the gear your tank has). Once Seal falls off, I E4E. The reason I generally wait this long is because you don't really need the mitigation until then. I usually even throw a heal or two at the other tank as well.

With your current level of gear you will probably still need a ballad if the dps is not burning down the splits fast enough. Also use Shroud liberally. At 4700 MP or so I usually use Shroud at around 3100 MP. As long as I am not spamming Cure II it is enough of a regen boost to keep me sustained in the fight. Do not call for a ballad unless you are around 1500 MP.

Turn 2 - ADS 50% - Something is really wrong here if you are having to spam Cure II during ADS. The only time you might need to cast multiple Cure II is if the ADS is at 3+ stacks or the Tanks take multiple sources of damage at once. This sounds like you may be overhealing a lot here, or the other healer is not following a good rotation.

If I ever call for a ballad here it is usually at 1200-1500 MP and the BRD will Battle Voice it. Again, liberal use of Shroud is important here as you can usually get 2 Shrouds in during this fight.

Turn 4 - Double Dread. While you can Cure II spam the 2 Dread phase you shouldn't necessarily need to do it. Some of this is going to depend on RNG and how often your tank dodges/blocks. Generally, as soon as the 2 Dreads drop the MT picks up the second Dread then Hallow Grounds. I'll top him off with Cure, then right before Hallow Drops I'll Seal+Regen then E4E him. A Rotation of Cure II, Cure II, Cure while seal is up generally handles any healing issues and will allow me to sneak in a few free Cure IIs. In addition,

I time my Shroud uses so that it is coming off CD right around the time the second Dread drops. If you can time this during the same time as the MT has Hallow up it is the most beneficial, but I wouldn't sweat it if it isn't either. As Seal is falling off I will generally PoM and continue healing, then finally end up rotating to straight Cure II, with an occasional Cure if the tank is topped off. Now, depending on our DPS even with BV Ballad towards the end I am generally near OOM during the pulse phase. However, when our core group is on with all of our top dps, we can actually beat pulses and I usually have plenty of MP by the end.

Just a quick run down of T4 mana management.

P1 - I Cleric Stance + Holy until at around 3100 MP. I swap out - Shroud.
P2 - Seal + Cure, Cure II, Regen, Then Cure with an occasional Cure II when needed. Stoneskin MT right before the Dread drops.
P3 - I solo heal MT after spiders are fed. Seal + Cure, Cure, Cure II rotation. Once you get this timing down it is incredibly easy to heal. Shroud generally comes off CD during this phase. I save it. SCH goes Cleric Stance and DPSs with the occasional Aldo on the MT + EoS.
P4 - I E4E the MT. Pop Shroud once threat is established. BRD Ballads towards very end of the Phase. I am usually nearly topped off.
P5 - I heal MT. Cure, Cure, Cure II (no cds).
P6 - Second Dread drops. Tank Hallows. I Shroud when it is available. I call for BV Ballad at around 1200-1500 MP.