here's the fact why i preffer fire warriors to guardsmen: their guns have longer range than a stonethrow. so yes, when they are assaulted, they usually die, but that's why you have the Kroot, or Gue'vesa. you have your fire warrior squad sniping down enemies, while the Kroot go in CQC. the Tau are not well rounded, like the spehs marinesh or guardsmen, so you have to actually combine the troops to achieve maximum efficiency. you have the fire warriors, Kroot and Gue'vesa to kill the infantry, pathfinders, hammerhead tanks, and crisis/broad battlesuits for mopping up the vehicles. while no, their stats are not great, they allow for more difficult, and fun gameplay. i never had the same amount of fun with my guardsmen, because they are well-rounded (i.e. equally bad (unless mass deployed) in CQC and long range).
and here's my point of view: no army in WH40k is bad. some have less all-around infantry than the others, but that makes up for more strategy both in-game and before, when you have to arrange them in such a way that they are well-balanced, but do not eat up your entire points supply. well, that's my point of view, yours is different, i guess.