The members in this club are usually pretty quick to help a fellow bird player sort things out so others may have already chimed in, but just in case they haven't, here's my thoughts...
A .010 gap at the 8th isn't bad for a factory spec Eppi. However, if you want to slam the action you should really start with a professional fret level and a good nut job. You might have a high fret at the 15th, a fret level will cure that. If you want to try some other options before fret leveling I'd do them in this order:
1) Since the problem is only on the D string Theres a remote chance you could have a twisted string. Try bringing the D string to complete slack so the ball end is free to move. Now starting at the nut, grasp the D string with two fingers and slowly slide down to the bridge letting the ball end spin if it needs to. Once you're at the bridge the ball end should be pretty much in correct position. Now tune the string to pitch and see if the buzz is gone.
2) If that fails, take a close look at the saddles, they may be numbered, if so make sure they are in the proper sequence. If they aren't numbered you can try switching the D and A string saddles. If the D string problem goes away then you're free to move on to a lower action. If the problem just moved to the A string then put the original A string saddle back in the A string position and put the offending D string saddle back in the D string position and visit a luthier for a fret level.
Thank you. I will try that with the D string. I already switched the A and D saddles and that did help a bit.