With 330 hours on Reaper and all due respect, you seem to be missing a lot of key problems of Reaper. Considering you even admitted yourself that you have no idea how much damage Reaper deals, I don’t think you are very eligible to suggest changes to how he works
The reason why Reaper is inconsistent and why he sometimes oneshots things well away from him is because his headshot is binary. See here for more info
This is what needs changing first and foremost.
Second, Reaper’s damage is fine. FYI he does 7dmg x 20 pellets = 140 damage at point blank, so both of what you suggested would be nerfs. The real problem of being ineffective is that he is hopelessly ineffective against armor, which should have been dealt with long ago by either increasing the damage per pellet while reducing the number of pellets, or allow him a new passive to treat armor as normal hp. This would not increase his effectiveness against dps but is much better against tanks.
Reaper does not need any form of nerf. He is hopelessly outdated and his huge dps of 280 is made irrelevant by the fact that he is horrifically slow and has no in combat mobility, as well as a terrible spread. In fact, his spread can be reduced along with what i mentioned above and his lack of mobility would still render him inefficient