If the Elemental Plateau is too crowded for you, and you don’t have a problem killing Water Elementals that are Frost Immune, another really good spot to farm them is in Skettis in Terokkar. You need a flying mount, and there is a spot in the southeast corner of the map that is a plateau way up high, with a lake. Personally I find the mobs (birdmen) pretty tough, but the water elementals around the lake…especially near the top of the waterfall…drop motes of water at about the same rate as the ones on the Elem Plateau, and the place is usually much less crowded.