You can find The Escape from Durnholde dungeon within Caverns of Time, Tanaris.
The coordinates are (64.2,49.9)
Free Thrall from the downstairs prison and follow him out of Durnholde Keep. When you leave the 2nd boss Captain Skarloc will appear.
1. Lieutenant Drake
/i Deals physical damage. Run away from Whirlwind. Attacks can reduce targets healing received & movement speed. Exploding Shot hits player stunning them & deals fire damage.
2. Captain Skarloc
/i Holy Shield increases his block chance. Cleanses his allies & grants them armor. Interrupt Holy Light. Kill Durnholde adds quickly.
Heroic Differences: Move from boss when uses Consecration, lands under him.
3. The Epoch Hunter
/i Avoid frontal cone Sand Breath. Inflicts ticking shadow damage to a player. Wing Buffet damages & knocks back all nearby.