The problem with pushing those duties off onto your co-healer, as I see it, is that you don't actually have much of an effect on the power of their heals. I'd be fine being second fiddle to my co-healer if I had the tools to make them better at their job. If, for example, A. benefic buffed heals received for one of the Sects so that the WHM/SCH had an easier time being the "Main healer", that'd support that style of play. As is, you're just pushing off more responsibility to your co-healer for more or less no gain.