well, generaly speaking, if your crisis suits are close enough to an enimy unit to use flamers than they are in serious trouble. they may be tough, but they just don't hold up in melee, and even with that 6" fall back move, you still will be assaulted on your oponant's next turn. which brings me to my second point, if you are playing tau, long ranged, sweaping, expansive battlefields are to your liking, city fighting leans more towards close combat and nitty gritty blood curdleing combat. you would probably be better off going with the space marines, rapid fire vollies and assault combat are right up their ally. the tau, and i am speaking from my own personal experience (you may have encountered an entirely different scenareo), just won't stand a chance against the melee happy enemies that haunt the blown up streats and destroyed buildings of the cities of death.