To me the solution is pretty simple. Nerf Indom to 300 potency, but make it's cooldown 1s, like Lustrate. The reason I think that's a good idea is because the current Indom feels too good, to the point that upping its cost to 2 aetherflow seems good, but doing so is also pretty restrictive. Nerfing the potency to 400 isn't really significant enough, barely putting more pressure on the other healer (or makes the SCH use one of their Eos cooldowns), and the lower cooldown doesn't really affect much in terms of common use (though Dissipation certainly gets better with it as a result). The main difference is in situations where Star/Assize is also being used at the same time. The amount of Indoms you may use varies quite a bit if you're coordinating with another healer's oGCDs.
I feel that change to Indom specifically is necessary because SCH has less AoE tools compared to single target ones, and while this certainly ups their frequency of use, it also puts more pressure on optimally managing Aetherflow overall, thus punishing SCHs for mis-using it more. And I do think it might be necessary to reduce the MP cost on some of their spells to compensate for this. I don't feel Miasma II or Physick need such a change, but Succor and Adlo might, and even then, a full revert isn't necessary, given Quickened Aetherflow does help a bit in that regard.