I have been a support main for the past few seasons in League and found it hard to comeback in close games as support. Shen is super strong right now imo. Your taunt is some of the best peel for an adc not only in the laning phase but within team fights as well. I was going to put who Shen was good against and who he was bad against but really, there is one defining feature. Shen is very good against the supports who try to stick to your adc and the smaller ranged supports and adcs. Fighting against longer ranges will prove challenging for any good Shen player. Other than that, matchups are highly based on the skill of your adc and the ability you have to poke with your Q.