I've played Tau for the past 3 years, and I absolutely love
apoc games. They are my favorite part of
40k by far. Based on about 10
apoc games over the past 2 years, here's what I typically run.
1) 9 Hammerheads.
- Always run these guys, in as many formations as possible. You know why, and those ork stompas will learn very quickly.
2) Individual suits
- Split these up into a squad of 1 suit and 2 shield drones. They will be much more effective as individuals and give less of a footprint. Typically I kit them out with 2 fusions and
DS them behind the biggest enemy vehicles. Make sure you talk with your allies and concentrate fire between armies.
3)Fire Warriors
- They've gotten better with the new codex and 6th Edition. I typically run a lot of
FW and use them to defend home objectives. Thanks to the (mostly) army-wide rule support fire,
FW can be a great objective defender. This will also allow your allies to bring less troops and focus on damage. As for markerlights, if you have the points add them. Extra markers never hurt. But they are one of the last things I add to my
apoc lists. Usually you can get by fine using the markerlights given by the
HH formations and pathfinders.
4) Piranhas
- If you have any, I would really recommend using them. Turbo the first turn for a nice cover save, then turn 2 use them to fusion apart any important vehicles. Great suicide units. Make sure you run them individually though.
5) Riptides
- I don't have any, but pretty much anyone on dakka will confirm that they are good. Run them as you usually do.
Unfortunately, I don't own the new
apoc book yet, so I don't know the new tau formations or which ones transferred. In my group we allow old datasheets as long as they weren't updated in the new book. If they let you, I would recommend "Pathfinders Long Range Infiltration". It's a stealth optimized devilfish and 1-3 pathfinder squads in devilfish. While you'll lose a
HH formation, it more than makes up for it. The stealth devilfish gives the pathfinders stealth field generators, the whole formation can be deployed 6" away from enemy models without
DS, and (best of all) if you have 3 markerlights on a model within
LOS you can use them to allow ANY friendly model hit on 2+ for the WHOLE TURN! This can be done multiple times a turn. One of my favorite formations to pair with the pathfinders' markerlights and the
HH formations. (Note: the devilfish replace their gun drones with marker drones for even more
lols)
I typically run 6
HH in 2
apoc formations, 6 squads of 12
FW, 18
BS with 2 fusion and 2 gun drones each, the Pathfinder formation, and a couple of piranhas. This usually puts me at right around 4000 points and is always fun to play.
Hope this helped!

Make sure to take pictures and post a battle rep. There aren't enough
apoc battle reps on dakka.