As it stands now, post 1.1.1 patch, here are the new approximate TTKs. They are all based off of a fully armored Titan (so the maximum TTK), and are assuming the shooter gets all headshots.
TTKs:
High Impact AR TTK = 1.06 s (previously .93 s)
Middle Impact AR TTK = 1.00 s (previously .90 s)
Low Impact AR TTK = .93 s (Let's be real, no one can get 16 headshots in a row with these things, so this is not at all useful, and the TTK is the same as before the patch)
High Impact PR TTK = .94 s to .83 s (depending on ROF)
Middle High Impact PR TTK = 1.00 s
Middle Low Impact PR TTK = 1.01 s
Low Impact PR TTK = 1.07 s
As you can see, the High Impact PRs are the new fastest killers, while the Mid Impact ARs and PRs still remain relevant. Low Impact PRs, and High Impact ARs are now the slowest killing weapons.
In my opinion, the damage nerf to ARs was unecessary, as the extent of the damage buff to the PRs has more than made them competitive. If it were up to me, I would keep the changes made to AR range calculations, so as to clearly define a role between them and PRs, and remove the damage nerf. This would provide High Impact and Medium Impact weapons from both classes with similar TTKs, and it would allow for distinctions between close quarters, and mid range combat. As it stands, the High Impact PRs are the clear winners in all areas, with little to no reason to use ARs.