You might try using a little extra overdrive/distortion. Also, when your in the process of a pull-off while tapping, don't pull-off straight back up, pull-off at a slight angle, so when your finger leaves the string your actually slightly "plucking" it with your finger. This will make each note a little clearer and louder.

When your dropping to D, it's less tension on the strings, so the taps and pull-off's take less effort, which makes it sound better to your ears.