Played a little with my level 4 artifact shadow priest. Very impressive rot damage (comparable, if not better to affliction) with great utility. But my god it really requires some excellent kiting skill and maneuverability to make it work if you're without a healer. It helped I was in temple so I wasn't focused that much, but classes like hunters and warriors were suddenly becoming a threat - I would just brush them off on my affliction lock.
One thing I like to do is impose group positioning by forcing my way in advantageous positions - something I can very easily do on my demo lock and to a lesser extent, my afflock. On my demo lock I can actually act as a bulldozer and push the other team away. Shadow priests must work in the shadow and cannot impose position due to their squishiness.
Spriest gets like 50x better when you get the talent that increases healing done from dispersion. It's literally a full heal every 2mins where you also get 90%reduced dmg and can't be snared. pretty op
Got a frost dk 99, gotta say loving her every moment. On my offtime, I will be working on a hunter. Hunter has always been my favorite class since bc days. SO heres to hoping I become a good bm hunter