It's worth looking at for sure. Too tight can pull the rear der in a bit but then you could compensate for that at the barrel adjuster I guess. a2p described the initial barrel adjuster position very well. For my SRAM XOs, the distributor told me to screw the adjuster in completely and than back it out 1 whole turn. I then pulled the cable hand tight and locked it down. That meant I could make small 1/4 turn adjustements until I got the indexing to run smooth.

Two other things come to mind: 1. Is the b-screw set correctly as well? 2. Is the front der cage set correctly as well? The front mech is usually 1mm clearance above the big chainring. For me at least, setting both front and rear mechs correctly are complementary to each other.