The main problem with healers currently is one action (Stone/Glare, Broil, Malefic, and Dosis) accounting for >70% of your GCD casts, which only increases as you level and become less reliant on GCD healing. This could be remedied with the following:

1) Reduce the duration of all DoT spells (Aero/Dia, Bio/Biolysis, Combust, and Eukrasian Dosis) - increases the number of casts in an encounter.
2) Incorporate AoE spells into single target - this could be done by adding falloff damage, increasing their potency when executed a single target, or granting a beneficial effect to self or a detrimental effect to enemy.
3) Reduce oGCD healing potential - replacing oGCD heals with GCD heals further reduces casts of Glare/Broil/Malefic/Dosis.
4) Just add another offensive spell - can be done by reintroducing spells such as Miasma, Shadow Flare, Aero III, and Stella or reworking previously existing abilities such as Fluid Aura, Eye for an Eye, and Disable.