Neglected - depending on your precise definition, I would have to say Shamans, Monks or Survival hunters. Simply because they have been given the least amount of meaningful attention that actually improved their gameplay or fixed glaring problems. If however you judge negligence by how well a class performs and consistency of performance - BM hunters take the cake, the cherry off the top, and a large dildo up their asses. There is basically no reason whatsoever to include hunters as a class in any progression content, beside loot itemization. Even then, this loot would be better spent on a shaman. MM is more or less decent, middle of the pack performance. But nothing that can not be done by a warlock, mage or a shammy. BM or SV are bottom feeders, being either extremely inconsistent (SV) or severely undertuned to the point of being almost useless even inside their supposed niche (BM).