As far as stat types, leather and mail are both split half-and-half for caster vs melee. This is a little iffy. In both cases, there are two caster specs (Balance and Resto Druid, Elemental and Resto Shaman) out of six total specs (Druids and Rogues, Shamans and Hunters), so it seems a 33/66 split would make more sense, but maybe they just wanted to keep it simple.
The case that really bothers me is plate, which is split evenly between caster, tank, and DPS (see right). The only plate spec that wants caster gear is the Holy Paladin. That's one of three specs from one of three plate-wearing classes, and yet it gets a third of the plate gear. I'm sorry, my plate-clad healing brethren, but that's just not an equitable proportion. Mostly it just means that our prot pallies have full healing sets and we're still disenchanting a good chunk of the plate every week. Here's hoping we see less caster leather, mail, and especially plate in Ulduar.