Then show your work. Show that over an X round encounter that the fighter using action surge and the ranger using swift quiver + your modified hunters mark do about the same damage. I don't think it's going to be close.
I'm amazed at the number of people who want to change things and don't even crunch some simple DPR numbers to check their proposed changes first.
Please don't make assumptions. This capstone change is the only thing I proposed as it is the only problem I see. An average of 4 damage increase for ranged rangers is very disappointing.
Here's my quick workup
So your proposal is 1d8+1d10+mod with advantage and swift quiver for the Ranger. That's 54.6 DPR at base 70% accuracy or 91% with advantage.
It has always advantage because hunter's mark. So please remove the 70%. (edit: misunderstood you there... you 54.6 is calculated with advantage).
Fighter with 4 attacks at base 70% accuracy does 26.6 DPR. With action surge it's 53.2 DPR.
Even with Great Weapon Master applying proficiency bonus damage the numbers don't look that much better.
Ranger 76.4 DPR
Fighter 43.4 DPR Action Surge 86.8 DPR
This is actually a good calculation why I think it is close enough.
Remember that the fighter can action surge twice per short rest.
The ranger can swift quiver twice per long rest. Swift quiver concentration can easily be broken.
You also forgot to factor in studied attacks.
You also made a mistake with the ranger when factoring in great weapon fighting. They only get it for half their attacks, as it explicitely does not work with a bonus action.
So the ranger is only at 65.5 DPR and the fighter is above your calculated 86.8 DPR Probably quite a bit above 90 DPR (a bit too much work right now to calculate exactly).
Probably the ranger will have a slight edge, because they can reliably have a +2 magic weapon (self cast) while the fighter has not. Although at that point I'd assume the fighter will also have at least an equal magic weapon.
And for the fighter we should assume higher probability to actually have great weapon mastery and probably also archery as they have more feats to play with and less demand to increase a second atteibute.
So overall, I'd say that removing the concentration as the capstone for the ranger seems spot on.