bin it and go back to 7800 if you want good rear shifting, Ive worked on hundreds of 7900 setups with loads of different cable options and none work as well.

Just wait for 11sp Shimano when shifting takes another dive. IMO shifting was best with 8 and 9 speed drivetrains.

Look 595 internal (std shimano) cable routing - 7900 - and it shifts like a dream, easily as good as the Ultegra sl on my other bike.
Its a different feel, yes but does the job and the hoods i find more comfy and i dont find the setup of it any different from any other Shimano 10sp.
Downside - the shifters seem to rattle far more than i'm used too.