fahrenheitSince Demoman's nerf you basically have to prioritize staying alive more than previous iterations of Demoman in the meta. Never be at the front to initiate fights or try to take fights 1v1 since the class turned into a big squishy babbu. Only play midrange if it's not a huge risk you'll die and if team is around you or if you have someone with you (most of the time).
Demo didn't actually get much weaker in 1v1s due to the nerf... Stickies that hit the ground before detting have full, instant, pre-nerf damage radius. With a scout +forwarding you your stickies are going to be ground stickies, not air dets. The nerf primarily weakened the ability to do mid range and long range damage.