Hi,
I grow all my Drosera's, in fact all my carnivorous plants, in the same mix. It is 2 parts peat: one part perlite: one part sand. This is a very open mix which I find most plants really like. Very few carnivorous plants like really waterlogged conditions; sure, some of the temperate Drosera's growing very stagnant bogs, but many will be growing on Sphagnum moss which is quite well drained even though it is damp. Many of the South African Drosera's, including slackii, grow in very sandy soil's in seepages or beside streams so they are very well drained but damp (not waterlogged!). I do find my slackii's sufferer during hot summers, but they are mountain plants so would probably prefer cooler, misty conditions.