Tanks and DPS optimise their rotations, tanks can optimise sharing their mitigations and DPS can optimise the use of incidental heals
Healers don’t have incidental heals (assize and star are exceptions) so basically if the DPS can replace a healer heal with an incidental DPS heal it’s always a gain to do so, then from there healers really only have ABC. Think BLM had non standard, GNB has “do AOE rotation to keep cartridges aligned”, and other things like that. Healers optimisation ends at ABC
you could either fix this by giving healers tank like rotation so damage optimisation becomes an actual factor, you could cut oGCD healing so organisation of GCD healing becomes a factor, or up the damage so the same as option 2 is achieved