Eastern Kingdoms:
Alterac Mountains Merged with Hillsbrad Foothills
Arathi Highlands 25-30
Badlands 45-48
Blasted Lands 54-60
Burning Steppes 50-52
Deadwind Pass 55-60
Dun Morogh 1-10
Duskwood 20-25
Eastern Plaguelands 45-50
Elwynn Forest 1-10
Gilneas 1-12
Hillsbrad Foothills 20-25
The Hinterlands 30-35
Loch Modan 10-20
Redridge Mountains 15-20
Searing Gorge 48-50
Silverpine Forest 10-20
Northern Stranglethorn 25-30
Cape of Stranglethorn 30-35
Swamp of Sorrows 52-54
Tirisfal Glades 1-10
Twilight Highlands 84-85
Western Plaguelands 40-45
Westfall 10-15
Wetlands 25-30
Kalimdor:
Ahn'Qiraj: The Fallen Kingdom (Unknown)
Ashenvale 20-25
Azshara 10-20
Northern Barrens 10-20
Southern Barrens 30-35
Darkshore 10-20
Desolace 30-35
Durotar 1-10
Dustwallow Marsh 35-40
Felwood 45-50
Feralas 35-40
Moonglade 1-70
Mount Hyjal 80-82
Mulgore 1-10
Silithus 55-60
Stonetalon Mountains 25-30
Tanaris 45-50
Teldrassil 1-10
Thousand Needles 40-45
Uldum 83-84
Un'goro Crater 50-55
Winterspring 50-55
Others:
Deepholm 82-83
Abyssal Depths 80-82
Kelp'thar Forest 80-82
Shimmering Expanse 80-82
Kezan 1-5
Lost Isles 5-12
(Outland and Northrend stay roughly the same, although with reduction in xp needed in the 61-70 and 71 - 80 levelling brackets alot of zones will be able to skipped by those so inclined)