I can't see Tau models assaulting a Land Raider since that brings them closer to what's inside, which combined with a Drop Pod squad and Gate Librarian being on their door step means pretty much losing the game.
Since Broadsides are so great now and people are looking at Sniper teams etc, I can't see any more than a single Hammer head in most Tau lists. That's a single S10 shot that will on a platform ideal for our Drop Pod attack in the first place.
I think GW is ensuring Land Raiders are still pretty tasty because so far all the new goodness they release for the Codex books in 6th edition can't do much against it.
RE: Burst Cannons on Hammerheads
The previous edition had a pair of Burst Cannons that was replaced by a single Smart Missile System. I haven't read the Codex yet but is this not still the case then?
IMO, there's not much risk to losing the game by sending a few Firewarriors off to nuke a Land Raider. I'd rather have a team of these guys (which are really cheap) hide out ahead of the rest of the Tau lines ready to run out and ambush an incoming Land Raider with sudden death, and subsequently get wiped by the passengers, than letting the Land Raider actually reach the Tau lines.
The faster that a LR gets opened up, the sooner the Tau army can work on killing the passengers and attempt to kill THEM before they reach the Tau lines.
Hell, the Firewarriors don't even need to assault the Land Raider. If they're hiding in buildings, ruins, or rooftops along a street, they can just hurl the EMP Grenades since they have an 8" range. That leaves the Firewarriors relatively safe from getting immediately assaulted by the passengers.
Burst Cannons and SMS on a Hammerhead are both a single Twin-Linked weapon.
Going by what the Scouts are like in Codex DA, it's likely they'll be cheaper. I'd like to see them get grenade launchers with rad grenades, at least in the Scout Bikers but also in basic Scouts squads.
This would encourage me to actually take them since lowering a target's toughness by 1 then hitting them with a full unit of Bolter Marines will be a useful tactic. From an all Scouts perspective, lower toughness will help boost the poor old Scouts hitting power.
It's hard to see which direction GW will go with regards to the current dregs of our Codex. Assault Marines still aren't worthwhile in DA armies really, whilst all Scouts armies might not even factor on their radar.
I think the Scouts will inevitably be cheaper and get Dedicated LSS's.
My only problem with a lot of 'Anti-Tau' solutions (like Whirlwinds) is that they're pretty bad against marines and MEQ are so prevalent that in an all comers list I'm not sure how much mileage we can get out of whirlwinds still.
Stormravens, Sternguard, Drop Pods however are all solid choices against most whatever you fight - so there's definitely mileage from them as ever.
I think people put too much value on good AP and devalue the ability to cause tons of wounds for cheap.
Whirlwinds are pretty cheap and they can drop S5 pieplates every turn. If you hit a Marine Squad with one of those you can probably kill a couple every turn.
I think people also just generally devalue AP4.
Scouts, Necron Warriors, IG, StormTroopers, Firewarriors, Pathfinders, Kroot, Scarabs, Gaunts, most Eldar, Dark Eldar, Orks, Gargoyles, Rippers, almost all of the Khorne daemons etc etc etc etc will all have a really bad time against S5 AP4 pieplates.
Whirlwinds being able to hit almost the whole table and able to hide while blasting people is pretty solid, especially for the price.
Granted, there's several Space Marine armies, but it's mostly just them that Whirlwinds are of minimal use against.