Amdapor Keep - Demon Wall - WHM tips please!?

[YanDere]

You're doing it wrong. Regen ticks for 150 potency every three seconds for 21 seconds. That's 1050 potency over the spell's duration. Cure1 is 400 potency.
Regen doesn't do as much burst healing as Cure1 or Cure2, obviously. But it heals for way more.

I didn't say "it's the most weak", I said "useless".
This is because you'll never need Regen, if the situation is bad you use Medica II.
Regen takes too much aggro, you lose far more than what you gain.
I never use Regen, never used against primals HM, nor in dungeons.
It's simply useless.
If you use Regen against primals you'll raise the probability of being hit by Ifrit's Eruption, by Garuda's little whirlwind or being closed in the rock by Titan.