Greetings, community. I have decided to power level a Druid. I am currently rolling him as a DPS, but I want to heal when I get to level 90. Is there any point in leveling where dungeons are challenging enough that a healer will actually need to have a constant input, instead of just healing once every 15 seconds? TBC dungeons, Cataclysm dungeons, MoP dungeons? What would you say gives a healer a challenge?