My take:
Run of the mill combos for healers are a huge nono in my eyes for a couple of reasons. Firstly, it’ll boil down to a negative mechanic that’s only there to punish when not done right, we’ve just got rid of Cleric, we don’t need another reason for a huge chunk of the playerbase to refuse to DPS as healer. Secondly, it’s sending the wrong message, healing is the most fluid of the 3 roles and combos don’t fit into that ethos. We need something positive to make people more inclined to throw dots/rocks. This isn’t that.
Your suggestion of better heal/dps synergy is a much better approach, it doesn’t need to be massive. Just a noticable nudge. Imagine if maintaining both Aeros gave you a Lily every 10 seconds, 4 sch dots amped embrace by 15%, or Earthly Star gained a 5% potency boost per enemy hit. None of these things would make or break much of anything. But they are tasty enough, entirely positive and fit well with ‘good play’.