Essential Dignity: 400 potency, that can scale up to roughly 1200 potency. (enough to almost fully heal, plus it can Crit) 40s cooldown.
Benediction: Maximum HP, equivalent to roughly 1500 potency maybe? 180s cooldown.
Tetragrammaton: 700 potency flat heal. 60s cooldown.
Lustrate: 600 potency. Can potentially be spammed up to 3 times for 1800 potency! 60s cooldown (based on Aetherflow)
So yeah, Tetra is more similar in terms of cooldown, but Bene is closer in potency, it actually sits somewhere in the middle but ultimately all those skills do the same job.
EDIT: All three healers have similar utility in their ‘emergency’ heals really.
AST: 400 potency at higher HP, 1000 or more potency at lower HP.
WHM: 700 potency with Tetra, Maximum HP with Bene.
SCH: 600, 1200 or 1800 depending on Aetherflows.
Basically, they can all do the same thing, but WHM takes up two slots on your hotbar to do it.
Earthly Star: 720 cure potency, and 200 DPS potency.
Assize: 400 Cure and DPS potency.
Plenary Indulgence: Only cures.
Again, Earthly Star does both jobs in a way. It uses a scaling mechanic, which I suppose you could attribute to Plenary Indulgence, but functionally, its a Heal/DPS combo.
So with Earthly Star and Assize, in both cases you would typically use the skill on cooldown for its DPS value, whereas Plenary Indulgence you'd save for cures. Hence why Earthly Star and Assize are more similar in function.
Asylum: 100 potency over 24s. Requires party members to remain within the area of effect, and chances are, they won't.
800 total potency (reliant on party members staying within the area for 24s)
Collective Unconscious: 150 potency over 15s, plus 10% damage reduction. Effect is imbued upon party members, allowing them to leave the area of effect. This means it only needs to be used for a split second to bestow this effect for 15s on all party members in range, you don't need to stand still. You can also extend the duration of this effect with Celestial Opposition and Time Dilation, increasing the effective potency of the HoT.
If you do stand still however, you can extend the duration beyond 15s, making that potency far better than Asylum, and with a damage reduction to boot!
750 total potency (guaranteed, can be extended to 1200 or even 1500 with both CO and TD, without needing to stand still, and even further if you do stand still)
But I thank you for your view, and thank you for not being too condescending about it, but it would appear that you don't quite "know every healing spell and what it does."