Well, based off of the simple fact that sch has the least amount of sustained hps it is by default the most gear dependent. It's hard to maintain the contrary when comparing sch to a whm who'm I'm pretty confident could solo heal most of the current content in 270 gear (provided a decent static).
This was readily evident when SB hit and tanks were pulling 60+ dungeons like they were running Baelsar's wall in 270s. Sometimes you couldn't even keep up with the HPS output required from some large pulls in places like Bardam's meddle (on SCH). This was way less of an issue on the other healers.
That isn't to say that you can't fill the gap with skill, but we are talking about leveling here afterall.