You can find The Culling of Stratholme dungeon within Caverns of Time, Tanaris.
The coordinates are (64.3,49.5)
To progress through the dungeon you need to keep speaking with Arthas. Check your map when waiting for the 10 waves and first 2 bosses to spawn, run around the middle circle to find them amongst the zombies.
Heroic Differences: Frenzy increases his physical damage done by 10% for 30 sec, also stacks.
2. Salramm the Fleshcrafter
Heroic Differences: Curse of Twisted Flesh reduces a players max health by 25% & inflicts shadow damage.
3. Chrono-Lord Epoch
/i Time Warp reduces attacks & movement of all by 70%. Wounding Strike inflicts damage & reduces healing effects. Curse of Exertion increases a players cost of spells/abilities by 100% for 10 sec.
Heroic Differences: On heroic Time Stop stuns all players for 2 sec.
/i Puts a player to sleep for 10 sec, any damage will wake them up. Inflicts shadow damage to a player. Vampiric Touch heals him for damage done with melee attacks. Carrion Swarm inflicts ticking shadow damage to players in front.