Well... anyone actually looking to this for advice, this list is pretty far off. Looks like it was updated Dec 7 for season 2. This is the POV of a support player, so take this from that POV.
Hog is a menace and definitely #1 with a Kiriko to cleanse him. Even without a Kiriko, he's got tons of HP and an easy one shot. Expect big nerfs in January, but if you can land hooks with him you'll climb. He really sucks to play against. He's so good you kind of have to pick him if you're playing competitive.
Orisa could be 2 as she's the only tank that can really stand up to hog currently. Her recent buffs made her a lot more viable. The damage fall off buff will make it much easier to secure kills, whereas it was a bit difficult to do with her before.
Doom got huge buffs that were active at the time of this article, but has since been slightly nerfed. He's still in a much better place than season 1. He's really hard to play, but you could arguably slot him in at 3. Just, if you play him, be aware of where your supports are or you'll just feed.
The rest of the tanks can depend on the map but are mostly viable with a couple exceptions. You can definitely win with any of them, but that's not really what ranking them is about.
Junker Queen is the worst in the game now. I don't think that's debatable. She's a ton of fun, don't get me wrong, but she cannot survive like other tanks can. With Hog being a must pick, she just can't come close to hanging with him. Orisa can also just bully her around since they're likely going to be fighting close to each other.
Ball is also fun, and my favorite tank to play, but unless you're some top tier Ball player there are way better picks. His problem is he's usually just not enough of a threat. I typically just try to dodge piledriver and ignore him as support
I'd put Dva, Zarya, Sigma, and Winston in the same tier. Winston is at the bottom though, because he just can't compete with Hog. The other three at least have some defense against him.
Rein is unfortunately a tier down from them, but better than JQ and Ball. He can do well on certain maps and in lower ranks, but as you climb you'll find him worse and worse. He needs buffs pretty badly, probably in the damage department.
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