How DPS complexity can make healers more forgiving

[Shurrikhan]

Sounds like [Legion/Dragonflight Druid's [New Moon][Half Moon][Full Moon]]

Was thinking more 0s, 1.5s, 3s casts, but yeah, pretty much.

Though not on shared charges. Instead, like Apex Arrow -> Burst Arrow, once you pop the first you just have a fixed amount of time (say, 6-10s) in which to use the rest (not refreshed on next skill's use). That way there's a bit more play (if also a bit more rope to hang yourself by).
With the appended universal change that skill-unlocks snapshot (cannot cancel your current cast when the unlock buff runs out) if using the lower unlock duration.