There has been a lot of talk about whether healers should dps or not during fights. This is not the point of this thread.
Rather, I would like to suggest some changes in order to make Healer's dps feel fun and rewarding.

WHM: Casting Stone IV grants lillies. Lillies increase Spellspeed for X percentage, stacking up to 3 times. They also increase potency of the abilities they affect.

SCH: Broil II applies a "Meltdown" stacking debuff for 5 seconds. Each stack increases the damage the target takes by 1%. Can stack up to 5 times.

AST: Malefic II applies a "Star Alignment" Debuff for 15 seconds. When a player with a card buff hits the target with said debuff, the duration of their card buff extends by 1 second up to a maximum of 10 times.

The idea would be to have healers contribute to dps in a supportive manner, either by increasing the damage the target takes, increasing their own healing efficiency or making their buffs more potent.