As with all our classes, Adam and I are pulling from as many sources as possible to get a clear idea of what a Barbarian or Druid is.
For the Barbarian rage would certainly be a core option, but not the only one. I recently read an early Chinese account of the savages to the north and thought "those are totally Barbarians" which led to the idea that I think we'd put at the core of the class: you're not from around here.
Our working draft was a core move that gave you a list of things that are true of your homeland but not true of wherever the game is taking place. Whenever you embrace one of those traditions you get a benefit, or you can abandon them. Each one you abandon gives you 1 XP, but once you've abandoned them all you can't gain new Barbarian moves.
To me that's the core of the class, that's what make it not just a Fighter. On top of that we'd add some moves that reflect other typical Barbarian tropes: high HP, low armor, and the ability to turn damage taken into damage dealt. We also had some stuff about shaman-ish magic, just for kicks.
The Druid on the other hand has two very different drafts right now. (We've started working on it more since it has such a massive lead in votes.) Shapeshifting is core to both, of course, but the way magic flows with each changes.
In one of them magic and shapeshifting are two different things. Shapeshifting lets you take on any animal form and magic is based on the land you'ev bonded with. We're being very careful to make the land bond not a restriction, since being a Forest Druid in a desert shouldn't suck.
In the other draft shapeshifting and magic kind of flow form the same core mechanic. in this version the Druid is all about seeing the magic/spirits in things and being able to work with them. This can mean learning their form (shapeshifting) or having them act on your behalf (entangle, for example).
Anyway, those are the thoughts going on right now around DWHQ. We're constantly trying to nail down what we think the essence of a class is, and these two provide some real challenges. I'm excited to see how the winner turns out!