I'm sorry, but I have to disagree with the fact that you need an off support. Double main support is often a good comp.

I don't like Ana Moira, but Ana Baptiste or Moira Baptiste is fine

If you are running a Pharah, you most probably want a Mercy. In these comps, it is very beneficial to have another main support to heal the tanks, so that Mercy can focus on the DPS

Having any combo with only Brig, Zen or Lucio is bad, yeah. Not enough healing. But you can make a solid composition without any of them

I understand the benefits of a defensive ult, but giving up a defensive ult for a stronger neutral fight is a fair trade, a lot of the time.

My point was more that supports don't pair like tanks do. With tanks, your first thought should be what your other tank is running. With supports, your first thought should be what the rest of your team is running, usually building around the tanks. Some supports are useless in certain comps, for example Mercy in deathball, seeing as she doesn't have any GA targets, or Moira in dive, seeing as she has no way to heal a spread out team

I didn't mean to imply that any support combo can work, just that there are more important things to think about. With Baptiste specifically, you can run any other healer with him