Nah i disagree that a Drumset is one instrument. I think thats saying that an orchestra with violins, violas, cellos, bass violin, trumpets, trombones, french horns, harp, and the entire percussion is one instrument.
You can use 2 stereo mics to capture the entire peice, or you can use mics for individual section. Its not a matter of right or wrong just what kind of sound you are looking for.
A snare is a totally different instrument than a tom, cymbal, hi hat, bass drum, just like a violin is totally different to a trumpet or cello.
Individual micing is probably a little more difficult, different sounding, but it isnt wrong. Most of my favorite Rock Drum recordings were done with very close micing techniques and the overheads used mainly for cymbals. In my opinion it give you more options later because you are breaking down the instruments.
danny