OB50 Tierlist

S Tier:
Makoa is the still the best tank. While the OP Half Shell reset build was nerfed and his hook was nerfed, he's still much too good to pass on due to his relative tankiness, ability to displace enemies with his hook, and pretty strong shielding.
Androxus is definitely the top flanker. His DPS is very high his mobility is second only to Evie when using Dark Stalker, Heads Will Roll can quickly burst any unsuspecting champion, and Godslayer + Power of the Abyss is just too good of a combo.

S- Tier:
Inara saw a huge huge buff in usability and it bumped her all the way from the garbage heap to one of the top champions in the game. Her wall is very good for blocking off flankers, Warder's Field provides good point control, but her main reason that she is so good is that now the Mother's Grace legendary provides debuff immunity, which is crazy good and can counter so many things.
Bomb King is still very good even after all the nerfs. He still has high DPS with splash included, awesome point control with Grumpy Bomb, and easy escape with Accelerant + Poppy Bomb
Drogoz is still top tier with his insane damage potential along with splash, his ability to shred through shields, his fire spit which combined with Combustible makes for great point control, and a nice OKO ultimate. All three of his legendaries can be used to full effect and are very strong, making him very versatile and able to adapt to any situation.

A+ Tier:
Seris has become the best support due to very strong single target healing, awesome damage capability along with the legendary card Agony which is very annoying to enemies, and one of the best ults in the game that can be comboed with almost any other damaging ultimate. She is also the most survivable champion with Rend Soul able to heal a ton of her health and Shadow Travel able to allow her to escape easily out of any situation.
Lex is a very good flank that can also be used as a damage. He gets a lot of credits to by useful items, has good damage, and his right click can easily finish off enemies. His mobility is also often underrated but 3 seconds on a pretty long slide is insane.
Barik saw a fall in the tierlist due to a relatively uncalled for shield nerf. Although his shield build was very good, it wasn't used that much and now his shield has low uptime and isn't as effective. He is still a very good that's good all around with decent damage from his turrets + blunderbuss, okay shielding, good mobility and a great lockdown ulitmate.
Sha Lin's pure dps seems quite low, in fact, it's the second lowest of all damages, only in front of Willo. However, add the fact that he has sniper's range, a stun, one the best escapes for a damage in Withdraw, and huge damage potential in planted, he's easily one of the top damages. However, he's often outclassed in many situations by splash damage dealers and blasters and is more vulnerable to flankers that the aforementioned champions.
A Tier: 
Mal'Damba may not outclass Seris's pure healing, but he is definitely better for dual tank teams with his Mending Spirits having a short cooldown and no channel, his gourd being effective for area control and area healing, and an pretty useful ultimate that can be used to scatter enemies or comboed with another ultimate
Fernando used to be a pretty good tank, and fell flat in recent patches. However, as of OB50, his scorch loadout is pretty good and he can be an effective zoner
Cassie has 2 strong legendaries in Exaction and Big Game, and good damage as a result. Her ult is useful for teams but not so much for random matches.
Viktor has always been a solid damage dealer and can make a heavy impact if used by players with good aim. Firefight makes hip firing a solid option now but it's not as easy to hit shots as using Iron Sights
Ying While some may argue that Mal'Damba is better than Ying, I still think they're around the same level. Mal'damba can probably heal more efficiently, but Ying can deal more damage and is still useful after your opponents get Cauterize 3
Ruckus is still a bad solo tank. He's amazing for dual tank team though due to the damage he adds while also being able to hold point.

A-Tier: 
Willo has tons of burst damage with Seedlings, and has a great point control ability with dead zone. However, she has somewhat low pure damage, a bad ult, and is easily countered by too many champions (Viktor, Tyra, Androxus, Lex, etc)
Pip has always been a very flexible champion, but sometimes that flexibility hurts him because he doesn't excel in any category. He can be a decent healer on dual tank teams, a decent damage dealer with his splash damage, and a decent flanker but he's not top tier for any of these. His ult can be game changing, however.
Evie had a bad streak where she was one of the worst champions in the game. In OB50 however, she's a decent flanker with her Reprieve loadout.
Buck was pretty overpowered before the Bounce House nerf, mainly due to the fact that he could make mistakes and escape without punishment. Now, he still can but it's a little harder with the health nerf and most other flanks outclass Buck due to his long TTK and very short range.
Kinessa While good Kinessas can light up the enemy, she's way too vulnerable to flankers and can be shut down easily by most champions and hindered by shields. Her legendaries also are pretty bad, with Steady Aim forcing slow, rhythmic firing, Eagle Eye headshots being inconsistent, and Oppression not really affecting too much other than slowing flankers down a bit.
Tyra has all the abilities that a damage dealer would want with high DPS, point control in Fire Bomb, and flanker control in Nade Launcher. However, she can easily be killed due to her lack of movement ability and she has a bad ult, dropping her to A- Tier

B Tier:
Grohk had a few patches to enjoy his time as an awesome damage dealer using Maelstrom, but now he's back to being a mediocre healer and only has average damage with a bad ult to go along
Grover is actually out of D tier due to a a semi-decent root loadout! That doesn't really compensate for how bad he is in general though.
Torvald After enjoying a brief period of being good, Torvald was nerfed back down to B tier. Now he's easily killed with wrecker and has no movement, and his ult doesn't really do much on many maps.

C Tier:
Maeve still has her burst damage, but any aware player will easily kill her, she has a bad escape and now has zero sustain with no more healing from Nine Lives

D Tier:
Skye Is an explanation even necessary?