My Healing Priest really hasn’t done much in the way of quests all through her healzorz life.
I started healing full-time for PUGs of complete strangers at about level 35 after having traded run after run with various friends of mine to get her up to that point while she was a toon that I didn’t focus on very often and mainly only played to burn off rest bonus here and there.
PUGging worked great (especially those late-night ones) all through the 30s and 40s, but once I got to the point where Blackrock Depths was the main instance to run through, things slowed way down, and I finally bit the bullet, went shadow for a while, and ground my way from 52 to 58.
Once I hit level 58, I re-spec’d back to Holy/Disc and started healing Ramparts and Blood Furnace runs in Hellfire Peninsula. I didn’t touch a single quest in that zone (not even dungeon quests) until after I had reached 5999/6000 Friendly with them, and then a quest-turn in from a drop in Ramparts brought me over the boundary to Honored.
After I finished getting to Honored with Thrallmar, I was ready to hop into the Coilfang Reservoir instances, and then into Auchindoun, and up and up from there.
I lived in instances throughout my 60s and, once I hit 65 and started planning for my level 70 gear, in the PvP battlegrounds as well.
Why Holy/Disc Priests Are Generally Poor Solo’ers
I’m sure it’s no surprise, but a character like a healing priest with very few points in the Shadow tree aren’t anywhere near as uber as most other characters in the game when it comes to questing and in particular, solo questing.