I can't really speak from a healer's perspective, but as a DPS I really only expect the healer to chip in after 50 and basically just on dungeon trash. Tanking up through 47 I've felt about the same way. If the run is actually going slowly for any reason other than people dropping dead it's probably not the healer's fault. That said, come 50 just running into a group of trash, switching to CS, and tossing out Holy a couple times is incredibly useful and I'd think fairly simple to pull off. Tank will likely take almost no damage since you're stunning everything while you do it.