This is my first real attempt at the horde side. Is this information still accruate? Are there other spots I should also visit in addition to this? BTW this is on a PvP server so don't even mention STV or TM, I am looking to minimize unwanted ally interaction and maximize exp per hour.

15-20 - The Barrens - Harpies *
15-20 - The Barrens - Bristleback(s) *
20-25 - The Barrens - Bael Dun Exavs *
22-26 - Thousand Needles - Galak Scouts (etc) *
25-30 - Thousand Needles - Grimtotems
30-38 - Shimmering Flats - All monsters. *
38-40 - Dustswallow Swamp - Very North East Islands, Murlock Warriors/Oracles.