The problem is with the pads you are using . The Ds2500 are a nightmare for leaving patchy transfer on the discs , which gives you a warped (not straight) disc feeling . They aren't abrasive enough then to clean the disc afterwards unless you do some brutal braking.
You need to buy better pads eg: the carbone lorraine RC5+ , best road/track pad out there.. .They are abrasive enough to ''clean'' the disc so no transfer problems but wear them prematurely..
Spend more on the pads and less on the discs..