Healing will never be "enough" when it's choreographed and predictable.

You can plan everything out and current healer design doesn't support constant GCD healing output.

The only things that may need constant checking is boss crit autos.

There's really no way around it. Esuna is generally one-dimensional and Throttle is bad example IMO.

The reason some 1 healer runs aren't possible are certain mechanics that require two healers or the mechanic being too unpredictable with targetting a pseudo healer target.