Like Dr. Wurm, I just use whatever I can get. Nepenthes aren't picky so I don't make much of a big deal out of it.
Right now its
Sphagnum:Peat:Perlite:Vermiculiterchid bark:Ceder mulch
2:2:2:1:2:1. Yes its weird but it seems to work...
I've lost my first two cuttings from rot in pure LFS mediums, so I won't be using it again and I always repot Nepenthes I receive that are potted in pure sphagnum.