Well I clearly remember reading somewhere that JKR wrote the epilogue early on, while she was writing the first book, I believe. Which in my mind, explains why it's so weirdly contradictory in places. I think in the beginning of the series, to her Slytherin really was just a one-dimensional house of baddies. JKR's writing as a whole improved throughout the series, and I think along the way she did realize that everything has layers, even Slytherin. But the epilogue had already be written, so.

Noelle // Slytherin // 9