So I got bored at work and decided to make a tier list.
This is based on my own experiences and how I feel/see heroes doing at higher levels of play:
S tier: Can adapt and perform well against any comp/situation. Lucio's backwards wall ride vastly improves his maneuverability and survival options. Eveything else for the hero, including speedboost and sb are invaluable to this day. Roadhog at higher levels of play has too many tools to be a huge asset. As long as there is a shielding tank, he is nearly unstoppable when played well. The counters to his hook are shredded by right click, hooking and killing has become so consistent 200 hp heroes will never survive and tanks will likely die immediately as well (ironically the damage out of hook means that if your dps works with you, you actually may want to hook first in a hog fight). In addition to dealing sizeable damage and one shotting at 10-12 m. He is almost a necessity on any team.
A tier: can be played in nearly any comp without needing to switch to remain effective. Mei is iffy to me, but I do believe that her damage output/cc/shielding is far too good to ever consider her a detriment to the team. On the whole this tier shouldn't be too surprising other than Mei. The heavy reductions to D.Va have brought McCree back, and while he is not as good as 76 in many comps, he excels more against dives focusing on Winston/Tracer over Soldier. Ana remains the best healer in the game.
B tier: can be very effective most of the time but requires some synergy and possible switching if situations turn sour. Winston is at the top of this tier, as he has risen greatly with D.Va falling off the chart. Playing around Hog is not too bad for him, as long as he has support from other divers. Sombra in the third position is due to the massive buffs hack has received meaning more support to the team in actual fights. In addition, EMP still wins fights easily. An underrated hero, albeit one with one of the highest intellectual barriers. Reaper may rise more, but Hog actually makes life surprisingly difficult for him, esp with support and healing from Ana.
C Tier: heroes based on momentum. They can work if you are extremely proficient with them, but almost always have more preferable choices in most comps. Hanzo is above Widow as he has sonar arrow (whereas venom mine is near useless), can defend himself, and can provide more consistent damage and a more mobile team than Widow, who causes her team to play much more slowly and hope she can land shots. Mercy's res can turn things around, but so much hitscan makes her life much harder.
D Tier: extremely situational. D.Va was hit hard by the nerfs. Armor reduction means that soldier can tear through her with ease, she's less of a hard counter to winston, and she can't shield/stall nearly as well in the last few meters of a push. She also deals less damage overall and will generally not be able to get away in time while retaining mech. Junkrat remains purely situational in most matches. Torb, while still good, cannot fight off a tankier comp. In addition his turrets only serve to feed Zarya charge and are not as much use in a fight as they would be against squishier comps. Armor is nice, esp with Sym, but is generally not worth the trade off in dps and support slots.
F Tier: Bastion. When played at the same level as the other team, the team with Bastion will lose purely due to mobility and focused fire. Needs more tools. Hopefully the upcoming patch fixes this issue.
Again these are my views based on how I see the game/what I am seeing at the moment. If you have any questions, feel free to ask.