After some grinding, I managed to hit Masters 5 on support, which is around the range of what I was before the transfer from Overwatch 1. I also managed to get the starting flex support on my colleges D2 Overwatch 2 team, so I'm very excited about that! Anyways, after a good amount of experience with all of the support heroes, I feel decently confident on my tier list of all of them.
EDIT: Baptiste can probably be A now that I think about it. Immortality Field will be Immortality Field and his ultimate is very strong at securing and turning fights with how fast he can charge it up.
Lucio is incredibly important to most compositions with how valuable speed boosts are now in Overwatch 2. His survivability compared to the rest of the support roster is noticeably better with his amazing movement options alongside a knockback ability on a very short cooldown. His ability to peel reliably for the other support is integral to his viability as well. This is all without mentioning Sound Barrier, too, which on top of already being a great ultimate got two nice buffs; its cost was reduced by 12%, and as an indirect buff, it provides overhealth now instead of temporary shields, which grants half of the charge that regular health would grant.
On teams that Lucio may not be considered needed,
Zenyatta, while not necessarily required, is an very strong pick mostly thanks to how powerful Discord Orb is, especially now that there's only one tank. He's a great pick on compositions where the main goal is to poke them down rather than rush or dive them, though his main bane is how vulnerable he can be due to his wide hitbox and lack of movement. Snap Kick helps a bit with that weakness, but he's still decently prone to most heroes that are currently meta like Genji and Sojourn, but his strong kit makes up for it.
Kiriko, while isn't available in ranked yet, feels like she'll be a very strong pick in competitive play. Her self-sustainability and movement is great with Swift Step, and as the only hero with a cleanse ability, she'll become a nightmare against heroes like Junker Queen and Ana. Her ultimate is one of the strongest ones in the game as well with how much value you and your teammates can get out of it. That being said, though, it's difficult to get maximum value out of her due to her difficult playstyle to master, especially how precise you'd need to be with her Kunai and her below average healing output. That being said, Kiriko is a strong contender for one of the best supports in the game with her high potential.
Ana quite literally has two of the strongest abilities in the game in Sleep Dart and Bionic Grenade, both being able to greatly turn a fight when used properly. Nano Boost is also very reliable in securing fights; especially in Overwatch 2, you oftentimes don't even need to combo it with another ultimate to win fights depending on the circumstances. Her main drawback is how vulnerable she is as a target, and while her abilities can help against rushes and dives, forcing them on cooldown often opens up big opportunities for the enemy team to capitalize on it and win the fight. The fact she can only provide single-target healing, while still has a strong output, can sometimes be troublesome on certain compositions.
Baptiste can be a strong pick on compositions that tend to stay more grouped up thanks to is good group healing ability. Immortality Field also is still a strong ability in Overwatch 2, and his ultimate is very flexible in how you can use it, whether it be to initiate a fight aggressively or to use for yourself to increase your healing output in a pinch. With how long of a cooldown Immortality Field has, though, Baptiste can have some trouble when the enemy team is hard focusing one of your teammates once it's forced on cooldown, since his single-target healing is not exactly the fastest.
Moira has the strongest group healing in the game and one of the best self-sustainable heroes in the support roster, but when it comes to a need for utility, most support heroes are a better option than her. Her healing resources can oftentimes run out quickly under a lot of pressure from the enemy as well, so that becomes a major weakness for her. Regardless, her shear healing output still makes her a decent pick on teams whose goal is to rush in and win the fight as fast as possible.
Brigette can be a good pick for compositions that would want to stay grouped up as well thanks to Inspire, and her Repair Packs prove useful especially for teammates like Genji and Tracer that enjoy the passive healing while dismantling the enemy. Whip Shot and Shield Bash are also great for chasing down enemies and peeling for your teammates. However, it's very easy to overwhelm her now, since her passive healing isn't quite the strongest against burst damage and she lost her very reliable stun, and her ultimate got quite nerfed now that it provides overhealth instead of armor now.
Mercy is definitely the worst support hero by a decent amount. Her kit is very hard to get value out of reliably when better options are available. Her lack of self-defense without completely forgoing why she was picked in the first place is also a great bane. It honestly feels like that for her to get the most out of her utility, her teammates have to pour in their own resources that could be using elsewhere. I wouldn't call her a massive throw pick like how Doomfist is currently, but I just feel like she's very weak now compared to rest of the support cast, especially how the playstyle and pace of Overwatch 2 honestly goes against her somewhat.