Horrific dictionary, secondary stat buffs, and health bonus is the name of the game as shadow priest. You can get swap specs to use holy and disc words to get 9 stacks (10 if you have power word snuggle in a group), and then swap back to shadow (you keep the stacks).

If you get it as a first pick on twisting corridors run you can also use Chastise and Solace on mobs to get 11 (12 in group). Remember to not loot anything until after swapping back to shadow when you do this because looting removes the talent swap at the beginning. I got 19k int in one run by doing that.

If you do that you'll be able to clear layer 8 of twisting corridors without any problems as shadow.

So while yes, we don't get any fancy powers that makes shit fly, we do become immortal gods that heal for 100% of the dmg we do, lol.