Cure is 400 potency, 1.5s cast.
Cure II is 700 potency, 2s cast.

2 Cures is more healing and less MP cost than 1 Cure II.

Design intent is likely that we Healers would use oGCDs for emergencies, Cure for patching up the Tank and Cure II when the Trait Procs to make it free and when we need bigger heals in fewer GCDs.

Problem is ... Playerbase wants to DPS. MP Efficiency is absurdly good thanks to constant Lucid and free oGCDs and Job mechanics.
So players end up spending as few GCDs on Healing as possible, disregarding the healing efficiency of Cure in order to spend more GCDs on DPS.

... Saying that gave me a rather stupid idea.
What if .. Glare/Broil/Malefic were oGCD with a 1 second cooldown, similar to how MCH Gauss Round and Ricochet work for their rotation. Cure/Benefic/Physik become GCD fillers, with DPS weaved between.
Cure and Benefic Traits for free upgraded Heals becomes a valuable proc.