I leveled Astra full Disc with only 5 points in Shadow for Spirit Tap till I hit 50, then I removed them and put them into Disc. Never had a problem soloing mobs and elites I probably should have had a group for and its easy to underestimate Reflective Shield. I have 2 sets of gear for when I play, my Heal gear which is in the Shed till I go to an instance or group, and my +spell dmg gear which I use to solo with. I have about 400 spell dmg at 70 in my solo gear which isnt that great but its worked for me well. Im about +900 healing in my healing gear which helps loads as well in groups.
I liked everything in Disc and it seems to be pretty good in PvP too, tho ive never went Offence in PvP yet to try it much, I usually heal. Power Infusion, Pain Suppression, Enlightenment, Reflective Shield, and all that stuff make you able to live longer and do some good damage.
My method may not be the "fastest" or the "best" but it worked well for how I like to play. Gave me flexibility to solo and not be shunned by PUGs when the time came I had to group and heal. Yes you can heal as a Shadow Spec priest, however 99% of groups wont give you a chance to as they immediately assume you cant, plus it does take a lot of practice to get it down right and a lot of attention as you will quickly go OOM as a shadow priest trying to heal if you dont watch. The biggest peeve of mine in the WoW community is most morons on the game believe you cant heal if you arent a full Holy Priest, Holy Pally or Resto Druid which isnt true. Anyone can heal well, the talents help considerably yes but if the player is good, talents dont mean a hill of beans.
