I would agree on mail right now only two classes use mail compared to a bunch of plate/cloth/leather users. Somebody who can use ranged weapons in at least one spec makes a lot of sense as well.
That said given we have had two of in a lot of ways same/similar class in a row blizzard tends to go with what the feel is appropriate at the time. DH and monks fill basically the same role in groups other than monk healers.
Whatever they make next better damn well have a ranged spec. The three added classes all being melee with no ranged options is getting a bit silly if they did yet another melee class.