If you go all Mechanized (Devilfish & Hammerheads), it is still - somewhat - possible. But as Nick stated, you're paying a premium for those vehicles as compared to the Eldar doing the same thing. And Eldar can fight their way out of a wet paper bag.
Still, Tau are a fun army with cool models. I wouldn't take them to 'Ard Boyz, but they're not Necrons either.