To beat buzz saw, your best off countering it with a more powerfull force. In early game as atredies, you can make lots of bikes. you can also use the bikes to pull buzzies into a larger force. Because bikes are much faster. Harkonnen buzz saws are the slowest anti infantry. As Harkonnen, Use tanks in later game. But for very early game, harkonnens best weapon against buzzies are buzzsaw's. As ordos in very early game, use dusites. Hit and run (unless they chase you). because ordos can regenerate their life. So if you hit and run, your damnaged dusties will get full life again. a good way to distract in early game, is use a few lasers. do hit and run. When they begin to chase the lasers, move dusties in ffrom the site and let them get attack while the buzzies are chasing the lasers. Thats all i can think of for early game. Good luck!