The remote should not have any effect on the channel changing speed. It just sends a code. I did read that there was some sort of update (mainly Michigan?) that bricked a bunch of DCT700's. Maybe some other update affected the speed.
Also, verify the XR2 is set to Motorola mode. Maybe the DCT is trying to decode the newer XMP code and is slow to respond.
To set Motorola mode on the XR2: Hold SETUP until the light turns green. Press the B key.