Those who are advocating Deep Strike, don't. Tau can have a stupid amount of Interceptor with S7/8 guns, the Raiders would be shot down before they could do anything.
Tau are without a doubt the most absurd army at the minute. The Beastmaster/Wrack list might do a decent job if you have enough Razorwings to absorb the fire. The trouble is, the Dark Eldar codex was a balanced army in 5th Edition. With the introduction of 6th, the change in focus and the release of Dark Angels and Tau they're now quite underpowered. They're not weak, there's still armies they can beat, but Tau and Dark Angels aren't amongst those I wouldn't say unless you're a much better player or have a tonne of luck.
1. Keep in mind how many units have interceptor and when used you are taking the weapon off like. At most the broadsides and riptides will be able to intercept and this is where the Tau will have problems.
A. Do Tau shot the transport or the guy hopping out. If at the guys you can do what jayne said and use the boats as cover save. The wracks will get a +5/+5 save which is enough to weather the interceptor fire. Tau can't deny cover saves at this point.
B. If they choose the vehicle. The blast will hopefully kill tau and again the blast really won't hurt wracks. They might get cover blocking los now. More likely it will give you terrain since tau can easily destroy a boat, +5 invul saves is advisable.
The plus side you are dropping units around 150 points that have some durability to them. With a 6" disembark you can help limit scatter etc. You should be able to luqidfy a few tau here and there. You are going to lose guys, but by overwhelming the interceptor units with like 8 deep striking units Tau can't prevent all that from landing in their face.
You stil have to be selective and have to concentrate on the weakest side of the Tau defense. Done this with old daemons and it has always worked rather well. Grant it you are doing it on turn 1 and it is half your army.
I would say beastmasters wouldn't be a good ideal. With a 6+ save and Tau wounding that squad on 2s and 4s I would suggest against it. Wait it would be on 2s due to majority tougness. That squad would easily get blown away.
Wracks, Grotesques, and SSlyth, the snake guy. Are all high toughness with fnp which makes them a bit more durable. A squad of Grotesques are not easily blown away.
Against most armies I would say jayne's ideal is an awesome one, but against you have no cover save Tau it really is not going to work. What is a cover save? Most ask that vs Tau.
I still think mandrakes are great due to the double strength 4 ap 4 shots.
Another tactic is build lance heavy range and try to out shoot them. You have the range advantage with -6". The riptides should be a problem, but you are cutting marker lights to 30" which will force him to move his marker squads. If he went missle sides it also cut him down to 30" and limits his range. The rest of the tau army will be firing at 24". Take advantage of your range and just lance them to death.
You can use venoms to shoot at fire warrior squads advancing up the field. If you deploy everything back field his riptides is the only thing that can shoot you. 2/3 deployments will favor you if you decide to out range them and out shoot them. Focus fire the mobile units and the riptide. Any unit on his side comes within range of yours blast it away.
The lady would come in handy which will allow you to redeploy.