Okay, so I'm going to make some wild guesses here on what, exactly, you mean by certain names for things.
HQ:
If, by 'guidance system', you mean the thing that lets you shoot at a different target than your squad, then you don't need one for your Shas'el (he/she isn't with a squad, after all). If you mean a +1 BS, then you don't need to twin-link your Plasma, since you will rarely miss with such a high BS, anyway. As for the Burst Cannon (?) and Plasma combo, I find it less effective than either the Missile Pod/Plasma or Cyclic Ion Blaster/Plasma combos. If you are looking for lots of shots, go with the CIF/Plas, if you are looking to take down large targets, go Plas/MP.
ELITES
I like this Crisis Squad a lot, but it's on the pricey side. Be careful with it, since it's a fragile unit for its cost (like all Crisis suits).
TROOPS:
Excellent--a big fan of this stuff. You probably don't need the bonding knife, though. Save the points and throw a multitraker or two on your Devilfish--it's nice to be able to shoot those burst cannons, after all.
FAST ATTACK
Pretty good, though 8 is always better than 6, in my opinion.
HEAVY SUPPORT
I'm guessing that this Hammerhead has a Railgun. If not, it better get one--best damn gun in the Tau arsenal.
That other 280 points?
Grab a unit of Stealth Suits--the full 6. They are fabulous, and can rip through infantry like a chainsaw through a picinic table. With your last 100 or so, I'd go with a Sniper Drone team, or something that can kill tanks. The big hole in the list right now is a lack of anti-tank. Giving 1-2 Stealths a Fusion Blaster can mitigate this somewhat, but they are better for anti-infantry, somewhat. You could trim your stealth suits to only 4, and then get a bunch of suits with Fusion Blasters and Missile Pods, which might help.
Also, it would depend on how often you actually face tanks. If infrequently, you might not need it.