While it is true that Tau can't outshoot you if it's firing line versus firing line, when you don't have any good targets to shoot at you start having problems. The best advice I can give you is to cut off his jumping areas, keep as many units as you can in cover, and for the love of the Emperor, keep your tanks away out of sight from his Broadsides. Be aggressive too. If a squad doesn't have a good shot, or if it has no shots, move it somewhere to keep his mobility limited. Autocannons on Devilfish, Lascannons on Hammerheads, Battlecannons on suits and Fire Warriors. Oh, and Basalisks are your friend, drop a pie plate of eternal doom on his suits that are flitting around behind cover.