I had one of every DW class in cata (cba to level my monk now) but i cant rank them by "fun" factor. Its more of a animation thing, as back then i played my female troll DW frost in "wrong way", meaning i had haste build. And damn that sexy troll lady whirled around. After faction changing it to female nelf it get only better, it felt like whirlwind of frost.
So whatever you play, play it as a real blue-skinned masterrace instead of hairy mongoloids, retarded hulks or what-have-you.