Maybe they are saving it for another class? There's some small water based skills here and there but nothing that defines a job. WHM used to be big on air and earth, but this expansion transitioned the job into a light/holy focused one. So I'm guessing the reason WHM is losing its earth/water/air identity throughout the expansions might be because Geomancer is in the works. So by the time it becomes a thing, WHM won't have any air, earth or water based skills in the arsenal to clash with Geomancer's concept. That's just my guess though.