I'm curious about Aun'shi, the new Tau Warlord in the upcoming Warpack. i've been looking at him and his signature squad and I can't figure out what makes them something I'd want to use. What is the benefit to their abilities?

I feel I must be missing something.

I don't think you're missing anything. It's not the typical "Combo" Warlord. From what I've seen, it's more like a set of cards that make your deck quite stronger. Armorbane is REALLY good. I haven't played too many games this far, but shields have stopped my work a lot of times.

Also, since he's Ethereal, he can use the Honor Blade, making this, in my opinion, one of the best Warlords to kill other Warlords. You can use the Event to make more than one attack with a bolstered unit, and you leave your Warlord to attack in the end so he can retreat to your HQ and prevent getting killed yourself in order to strike again next turn. You can make a deck with low cost Taus and use this Warlord and his signature cards to make them really strong.

Aun'shi's first ability is darn good. Armorbane prevents your opponent from using shield cards, so you're pretty much guaranteed that whatever damage you assign is going through. It takes the guessing of whether your opponent will use a shield card or not out of the game. With the kind of damage that Tau units and attachments can dish out, that is no small thing.

The forced reaction, though pretty much forces you to keep him at a planet for the battle and attack last with him. No doubt, to balance him because otherwise he would make shield card pointless all the time. One advantage I see is that if you want/need to get him out of there, you can just attack with him, still damaging or killing something, and then he is gone, no need to waste a turn retreating him. I actually think, all in all he is very good.

His signature squad, I'm not so sure. I think they are mostly going to be useful because of the ethereal trait. The rest of the signature cards support the trait very well. Perhaps they'll be others along the way.

Armorbane is fantastic, particularly in a hunt deck (in which your primary win condition is to kill your opponent's warlord). The forced "return to HQ" reaction of Aun'Shi and the four sig units is a necessary balance to such a powerful ability, but even this can be used to your advantage. For example, Aun'Shi never "just" retreats; you'll always get a swing on your way out of combat, should you have to evac.

The new Homing Beacon from Howl of Blackmane also works well with him and his signature squad, it turns out.