Have a Demo 8 from 2013. With RockShox Vivid RC2 reat shock and Avid Code brakes. DT EX1750 hubs. Bearings few months in the running, feel solid.
Every time I land hear the rear brake engaging slightly. Checked brake line, checked tightening of the caliper etc. must admit brake pads are running pretty close to the disc. But shouldn't be an issue?
Why don't you remove the shock from the bike, remove the coil from the shock, place the shock without coil back on the bike and cycle the suspension by hand a few times. You may be able to get a look at something you missed without actually riding the bike.
Shock+ spring mounted, hit bikepark. Think the issue is gone, or I was mistaken all the time, and that it is cablerub. Because the only thing I had was the shifter cable and rearbrake line rub the tire sometimes when the bike compresses (not on normal hits but only when compressed far in the available range)
Looking back a few vid's from before changing spring etc. showed the rearbrake was engaging before the jump, you coud hear a small shriekwhile being compressed by the kicker and at the landing.