A lot of soldiers seem to think it's 100% useless now...I can't really say, I almost never even pick up the class.
Also DHR at a high level pyro is restricted to babysitting sentry nests or playing a support role through reflects. A lot of high-level pyro players deem him an almost totally useless class. In pub matches, people cry over and over about "W+M1 Pyro 2 OP" or "axtinguisher/degreaser 2 OP" when in reality against any competent opponent pyro just gets blown to pieces by every other combat class before he can even step in range. Also I don't know what classes you're talking about him making "null and void," considering spy has a knife that makes him fireproof and reflecting soldier rockets flawlessly is HARD.
Speaking of classes, which ones do people main? My favorite is the pyro, although I have a bit more time with spy, followed by scout, demoman, and engineer. I'll occasionally pick up the huntsman if I feel like rolling a dice to see if I get kills or not.