control your derailleur hanger
Derailleur hanger is confirmed straight. I have a DAG-2 as part of my tool set.
I dont think you can adjust the tension/spring. I had a problem with a Shimano 105 FD. It wouldnt spring back to the inner position. A little well place race oil, and some movement of the FD solved the problem.
If your FD is new I would sent it back if it wount spring back to the inner postition, and you can move it with your hand ( that way you are sure its not the adjuster screw or cable that prevents it from moving).
The FD is running great, the RD is the problem
B-screw is adjusted according to the manual, with the top pulley resting 6mm away from the 23t cog.
Wow, that sounds very odd. The only time I've ever had issues with the RD shifting to lower cogs is when I didn't route the cable correctly from where it exited the barrel adjuster on the RD itself to where it cinched in the pinch bolt. But if your sure this is right (it may be different from 2011 Red routing, I'm not sure), then it just sounds strange! I can't imagine a faulty RD; I mean there's very little to go wrong.
Yeah this is a weird one. I've seen the same issue you speak of when routing the cable improperly, but I'm sure the cable is correct. The 2012 routing is pretty much the exact same as the 2011, they just shaped the 2012 version a little differently so the cable rests a little neater (more aero?). This type of indexing performance usually says bent hanger to me, but my gauge says the hanger is dead on and the old RD runs great. Seriously considering sending this thing back and just keeping the old derailleur that works.