I'm talking along the assumption that you would prefer that a healer spend as little time as possible on attacking, which if that's incorrect, then by all means correct me on that. And I understand the mentality of wanting to make decisions based on support and not based on damage. The tricky aspect about that point in particular is priority in this game is determined by how much you ultimately contribute to the fight per cast, and DPS is ultimately what determines which action is the "right" action, even when you're restoring HP. With that in mind, creating a support system that hides that healer's DPS output allows the job design to thrive in an environment where DPS is largely expected, because you can approach the support and recovery tools as support and recovery while the damage that is expected of your job is accomplished for you simply by engaging with those support tools.
When I talked about building and detonating an engine, I meant figuratively. Here's a very light overview of where I'm thinking on AST in this regard. Draw and Play are GCD actions. You can draw up to 3 cards and play them as you hold them. They apply effects like a 5% DPS buff, a 5% crit buff... all simple buffs, but you can only apply each card to one person at a time. Two people cannot have balance, and one person cannot have more than 1 card other than you (for soloing). These effects do not immediately occur once you play the card. Instead, you have another spell that causes all of your cards to activate at once, applying their effects to whom you played them on. You also have your buff window spell that can activate the card on one person and extend the effect to the whole party. Every one of these actions generates a star that will attack an enemy for malefic potency damage when you activate a specific OGCD action on yourself or an ally.
So it's not exploding a DPS bomb on enemies, but rather setting up your buff skill to be used at intervals after you've played your hand. Then you reshuffle your cards and start again.
In solo, what I meant by detonating these buffs in small bursts is you'd play a bunch of cards on yourself, activate them, use your OGCD ability, then hit Malefic several times to detonate all your stars and start over. But outside of soloing, Malefic use would be very minimal. There are other tools I have in mind, but that's the core of what I'm bringing up.
I know you've stated you're content with a 1 button DPS healer that just hits that one spell and that's it, but I was under the impression that if there was a healer that didn't have to DPS very much at all, that would be preferable for you.