At a 1000 points, there's a lot you can get away with using Tau given how cheap our stuff is, in general. I like this list in the sense that you aren't overspending on anything and taking as many toys as possible.
A couple comments:
1) How big a deal are flyers in your meta? If you only expect to see the occasional Crimson Hunter or something, you might be better off ditching the Quad Gun and using those points to buy more pathfinders. Hell, you could stick Skyfire and Interceptor on the Riptide and still have a fair amount of points left over to either fill out your Devilfish squad or something. Heck, you are one Quad Gun away from having an Ethereal, and they are pretty damned useful in a Devilfish squad, let me tell you.
2) 4 Pathfinders will live for about 1 turn before turning into vapor against anybody who has ever faced Tau. If you're only taking 4 of them, I might just suggest taking no markerlights at all and throwing everything into guns.
3) I've generally found that mechanized Firewarrior teams work better in pairs than alone. That said, this is a 1000 point game, so it might work. I'd like to see the squad a bit bigger, though. Indeed, I'd like to see both FW squads bigger.
4) General observation: the best thing about Piranha are the drones. Don't expect those fusion blasters to pay off often--I've found they tend to miss at the most important times. I *love* piranha, but I consider them harassment units and diversions more than actual workhorse units. In a list this small, the points *might* be better spent elsewhere. Your mileage may vary, of course.
So, in general: drop something to either boost your firepower (Ethereal/more FWs) or your markerlight output (more pathfinders). The Quad Gun seems low-hanging fruit if you don't see a lot of flyers, and the Piranha aren't particularly essential, though I love the little gun drones they offer.