Your shoulder and helm are BiS, the chest with Brigands and Deadshot is great for ST. All you really need in your setup is the Wits/DS chest to be all BiS azerite.
I wouldn’t worry about it too much. In a given key you should be doing overall (based on your gear), 25-32k DPS (depending on the dungeon ofc). That is more than enough to push into at least a 18 key assuming your mechanics are proper. Just finding a group to push that high with is the tough part.