So, for a 750 point list you need to think in 750 point terms. The opponents you face will be limited by the 750 point level, too, which limits the kinds of things you'll have to deal with somewhat. Furthermore, if the Tau have an advantage, it is that they have a extremely cost efficient access to good guns. So, to your list:
Cadre Fireblade (60)
Good, solid, cost-effective HQ. I, personally, prefer the Ethereal in a Devilfish with FWs, but I play an uncharacteristicall
y aggressive style of Tau (which works very well, by the way, but anyway...)
XV8 Team (114)
Shas'ui - Fusion x2, Flamer
Shas'ui - Fusion x2, Flamer
I like this team, in general. I'd say that, against the majority of vehicles you're likely to face at 750 (you will very likely see AV12 or less, but relatively few AV13+ stuff save from Necrons), taking a pair of Missile Pods instead of the Fusion would serve you well. This way you can also have them float close to your gunline and contribute their flamers to any overwatch that is needed. That said, dropping them isn't a bad idea, either. My only concern is that they have to come in from reserves and not scatter off target in order to do that. It creates a level of randomness you might not want to deal with.
Stealth Team (120)
Yaaay! This guys are golden at low point levels. I'd even throw a couple drones with them, if possible. Adding in the cheap pinning firepower and disposable wounds is very helpful.
Firewarrior Team 1 (177)
Devilfish - Gun drones, D Pod, Point Defense Targeting Relay
You don't need the Point Defense Targeting Relay. It just isn't very helpful--your guys will either already be out of the transport (with the drones disembarked, too) and get plenty of overwatch on their own *or* the Devilfish is about to be assaulted and there's nothing you can do about it with a couple lousy burst cannon shots.
Firewarrior Team 2 (135)
Shas'ui - marker light and target lock
Good team for the fireblade. Add in more FWs, if possible.
Kroot Squad (70)
10 Kroot - sniper rounds
Again, quite good for the points and for the point level. Infiltrate is much more powerful in low point games--much more room to hide on the board.
Pathfinder Team (74)
4 Shas'la - 2x rail rifle
Ditch them. With prejudice. There is much better stuff you can buy with these points. This unit, as is, doesn't have a lot to recommend it. It is fragile, it puts out limited firepower, it has too few Markerlights at too low a BS to make much difference, and it's a First Blood point waiting to happen.
At this point level, you can honestly get away with taking almost no markerlights. Most of those scary, crazy-cover-save monster units that everybody throws around can't really fit into a 750 point list unless they play Unbound. Furthermore, every markerlight you take is firepower you aren't using, and at 750 you don't have enough redundant firepower to make it worth it.
My recommendations for the spare points are as follows:
-Another Crisis Suit, rigged with plasma.
-Another bunch of Firewarriors to either fill out your existing units or buy a whole new one.
-Another pair of Stealths + some toys to make the Stealths extra mean.
-Another whole unit of Kroot (not exactly recommended, but they could be fun)
-A Broadside (which I *think* you can swing--haven't looked at the codex in a while, so I forget their exact cost).
As for the lone vehicle, I wouldn't worry too much. With Jink + the DPod, the Devilfish is a tough kill and it should deliver the FWs where you want them before it blows up. Just know that is *will* blow up eventually. As soon as the FWs are out of it and the Drones are disembarked (always, ALWAYS disembark the drones!), the enemy will probably ignore it in favor of more dangerous prey. Then you can use it to block LOS, tank shock, and harass.