Im no expert (at all) with respect to blending - I try to follow the guidelines in the excellent guide on the forum. *BUT - some of the most interesting blends Ive done have been the "Cripes. *3 bags with only a few beens in them. *Wouldnt it be better to have only 1 bag". Category :P
Now, I guess that arises for any one of many possible reasons but I think the scientific approach of "Hmm - what is this SO missing? *Let me add xxx to fix that" tends to turn every blend into the same thing - your perfect idea of coffee. *A kind of nirvana-ish sameness. *Random blends sometimes shout back "look at me!"....
Of course, once you find a nifty blend based on dregs, you can never quite reproduce it. *So Ive given up and just enjoy!