I mean a really good Lucio or Mercy can be different but picking a support because it makes the team comp look good is almost always a bad idea. Only really good support players can reliably stay alive (and still do their job) these days.
If enemy team wants to snipe Mercy they will snipe Mercy. Maybe it costs them 3-4 players, but they will get you. There is only so much you can do to survive :b
----
Today is the day of shit Diva's. Holding to that pick even when enemy picks Zarya and utterly fucking reks Diva's face in with sledgehammer over and over again.