Reaper NEEDS a rework (nerfs and buffs), everyone with significant firsthand experience with Reaper knows that. Check Choice's comments about the subject. 

Dev History Context: Blizzard devs first mentioned their upcoming Reaper's work 1 year ago in 2023, before Sombra and Cassidy's rework were even made. So once again in may of this year with some details and ideas. Since then they never said anything new about it, they just released the Mythic Skin and kept quiet as if nothing had happened.

TLDR: Bad hero design for everyone under new 5v5 fast-paced OW2 model, newcomers and average players in the enemy team struggles against him due to easy team kill spree with his kit/kill cycle, veteran skilled players outperform and counter him very easily due to bland rigid and predictable kit and weak Ultimate. There is no "meta" justification and barely enjoyable gameplay loop to keep playing Reaper in high-mid skill level matches. With "meta" justification I mean if you list his kit and compare him vs Genji, Cassidy, Vulture, Soldier 76, Junkrat, Hanzo and Mei, it's masochistic and tryhard to pick Reaper, they are much more versatile. 

It's even more evident if you actually play all these heroes and fight against him, then play as him (give enough time to develop decent skills and fight skilled enemies). 

Note: It's self-delusional to personally compare 2 heroes's balance, if your skill gap with them is too large.

Remember, the goal is to make Reaper "weaker" for low skill levels and "stronger" for higher level skill levels.

So, in matters of Rework Ideas, I think Reaper would IMPROVE A LOT with 5 Nerfs and 7 Buffs to balance things out:

THE NERFS

1. Decrease Hellfire Shotguns (HeS for short) cadency/fire speed by ~25% to 1.75 shots per second (current is 2 shots/sec) and increase the reload time to 2 seconds (current 1.5 seconds).
2. Add a Recoil Spray/Overheat Spread mechanic to HeS. Make the HeS suffer growing recoil or spread penalty due to overheat for each consecutive shot after the 3rd or 4th shot in row (wait until the Buffs for it to make more sense). I don't know which would be better gameplaywise: recoil or spread penalty; but I prefer recoil option. In the case of recoil, the 4th and following shots will have a strong recoil with a roughly predictable pattern (similar to Soldier 76). In the case of spread penalty, the 5th and 6th shot will have 6.5 and 7.0 degrees spread respectively (0.5 degree penalty per consecutive shot) and so on up to 10 degrees total. Reaper needs to wait ~0.75-1 second to fully cool or stabilize the HeS after maintained and constant gunfire. OBS: There there could be Skull icons/details in the HeS that fills up or glows more red (color may depend on the skin) as the HeS overheat/recoil. Punish the SPAM with HeS.
3. Decrease Lifesteal rate by 5% to 25% of damage dealt. Officially it's 30% now, but in practice it seems to be 28% of damage due to enemy's passive effects. Hold on again, wait the Buffs.
4. Make the Reaper's baseline movement speed reduced by ~10-20% while he reloads his Hellfire Shotguns. Lorewise it would make sense too, Reaper LITERALLY SPAWNS HeS out of thin air or his own body's biomass, so he is actually making an energy/stamina effort to reload.
5. Decrease his Death Blossom Ultimate's range by ~5% and give it a hell steam mark in the activation spot similar to Shadow Step (it will make more sense later); Hold, WAIT for the Buffs, I know it sounds dumb now.

Basically, force players to aim, focus, hold, and select their shots better and think before reloading (you'll be a sitting duck for about 2 seconds), make EVERY HeS shot count. Make Death Blossom positioning a bit more important due to the slightly shorter range. Make the Reaper player skill ladder wider and skill expression deeper.

I know some of these Nerfs sound too harsh, but hold on.

THE BUFFS

1. Increase the HeS baseline accuracy by ~5-10% (decrease the spread to ~5.75-5.8 degrees) and ammo capacity to 12, it will compensate the Recoil/Overheat mechanic and reward high skill players that wait to cool/stabilize them and land the shots. Alt fire (Right Click) with special cursed ammo (it spends double or triple the ammo) with 35 damage points and minimal spread (~2-3 degrees) for mid range fire. It doesn't need to be GOOD midrange firepower, like Cassidy, Hanzo, Mei or Soldier 76, just decent (roughly 33% of his close ranged damage, i.e: 108 damage per shot), instead of current practical average 5 or 10 damage per midrange shot. Note: By pure logic, these are TWO shotguns, so it make sense for each of them to have 6 shells, they are not double barreled shotguns, but semiautomatic/automatic ones, most real life shotguns have 6 to 12 shells capacity.
2. Add a Soul Lifesteal of 70 HP for each Solo Kill and 35 HP for each Team Shared Kill. In other words, reward Reaper players that KILL, not only do tactically worthless damage (which enemy supports recover in few seconds).
3. Increase Reaper's baseline movement speed by ~5-15%, Reaper needs to be faster to actually engage enemies in close distance. Also make quieter footstep sounds, it's just ridiculously stupid how much noise the Reaper's footsteps make, Hanzo and Widow are quieter than the Reaper, but they do more damage with better range and mobility? What hell?! It should be the exact opposite, heroes focused at close range firepower should be faster and quieter for their gameplay to be reliable and useful, it also doesn't align with Reaper's lore. Someone who is mid-long ranged doesn't need so much speed, because he can compesate the distance with good aiming.
4. Wraith Rework with better floating speed boost by 75% (instead of current 50% boost), faster casting speed (instant like Kiriko or almost instant like 0.2 seconds instead of current 0.4 sec) and allow Reaper to fly some meters above ground (by holding space with a limited stamina bar that does not regenerate), similar to Juno jump of Pharah”s jetpack. Currently, many DPS and Supporters can track (follow at similar speed) the Reaper's Wraith, which makes no sense, I've lost count of how many times I've died to players who followed me in Wraith form, sometimes even touching me from behind, Wraith should be FAST, only a bit slower than Tracer, Sombra, Soujorn or Pharah. Genji, Hanzo, Soldier, Illari, Vulture, Anna, Kiriko and Mercy players can easily follow you around in Wraith. Stupid af?
5. Shadow Step Rework with less obvious telegraphing (loud voice line "FLANKING!!" + huge red smoke trail) and huge vulnerability to headshots when casting (entering/leaving teleport animation). Decrease the casting time to 1 second (instead of current 1.28 sec), increase the invulnerability to 1.25 seconds (current 0.98 sec) a bit more than the casting time and make the red smoke less flashy and eye-catching. Consider adding faintly glowing, hellish clouds of steam at the spot or a 3-meter-thick cursed line of steam on the ground, extending up to 35 meters in the direction of the Reaper's teleport. Introduce slight horizontal variation (±1 meter) to the line's position, giving enemies a rough indication of where the Reaper will appear. Currently, anyone in 10 meters radius know you are coming and exactly where you will be appearing, enough reaction info to almost OHKO Reaper for mid and high skill enemy teams. Reaper is a top tier assassin (former war hero) in OW2's lore, why the fuck he has the dumbest mobility ability in the game? Honestly I cannot explain.
6. Death Blossom's Ultimate rework with an auto teleport as player aims where he wants to activate his Ult (similar to Shadow Step as well as Doom and Bastion's Ults), ~10% more baseline damage output, upfront one time instant self-healing calculated on 10-15% of current health of all enemies within Ult's activation range OR instant 50 shields which will last until the enemy break it or the Ult's end, 10% better Ult's walk-spin speed, add 50% knockback resistance and a 50% damage rate nerf if someone tries to stun or sleep Reaper, INSTEAD OF CANCELLING the Ult. Genji, Junkrat, Vulture and Cassidy's ultimates are much better, you can 3K very often and reliably, sometimes even 5K. Reaper becomes a SHADOW DEATH GHOST while in Ultimate, why the hell does he walks so slowly and physically collide with enemy gunfire and grenades if he's a ghost like in the Wraith? In Wraith's form he is immune. I think he SHOULD NOT be immune in Ultimate, because that would be BROKE, but he should be resistant to knockback/cancelling and have a bit of extra health leeway.
7. The third ability in Reaper's kit, a cursed smoke grenade that either penetrates enemy armor or weakens enemy damage or healing (not sure which), allows Reaper to choose between 2 options, like Moira's Orbs. Note: Reaper USES a smoke grenade launcher in his cinematic trailer. Reaper player's could press G or Alt (or any custom bind) to pick his grenade launcher (cannot shoot with HeS at same time, similar to Widow SMG), then right click or left click to shoot something like a "Soulcurse's grenade" with 25 meters range and 2 seconds detonating time, which either gives a 25% armor penetration buff by (right clicking) or 25% damage output or heal nerf (by left clicking) against all enemies within 5 meters of explosion range for 6 seconds. It could have a 12 seconds cooldown to make it fair. Junkrat and Genji are much better "close ranged" characters because they also have midrange attacks. Junkrat's grenades can bounce off and reach other rooms, his remote C4 is insane, you almost "OHKO" Reaper with a grenade shot + remote C4. Genji can fly and slash or throw shurikens.

Current Reaper? Kiss your enemy's ass or die. No second options. 

All in, it would make him a much better hero (less predictable and more skill-demanding).