Both can cross-class skills of same discipline category. For DoL it seems pretty pointless for now (other than for crystal/shard gathering). For DoH it's essential.
Don't think they've said yet. The hats were in 1.x as craftable items, but the rest of the outfits weren't in the game. Chances are they're craftable since the hats were.
AF hats for crafters were but the AF hats for Gathers were extremely rare drops from Hamlet. I always wanted the Harvesting one