Zul'Gurub is a nice place to farm gold,
- because many mobs are dropping the Hakkari Bijou's (Blue Hakkari Bijou - Item - World of Warcraft) wich can sell for over 70 gold each, depending on your server.
Ofcourse you could use them yourself, to gain reputation and get a nice achievement.
- Also, the raptors can drop the companion pet Razzashi Hatchling (Razzashi Hatchling - Item - World of Warcraft) wich also can sell for 80 - 100 gold.
- Once in the three days you can kill Gahz'ranka (if you completed Nat's Measuring Tape - Quest - World of Warcraft) , Ghaz'ranka can drop the (15%) Tome Of Polymorph: Turtle (Tome of Polymorph: Turtle - Item - World of Warcraft) wich can sell for 100 - 500 gold.
These three methods can add up to alot of gold!Atleast 500 gold / hour i would say.
Most of these goldfarming methods should be no problem for casters since the bijou's and companions drop from trash mobs, if you're able to kill bosses you could earn around 20 gold / boss kill.
While u're in Zul'Gurub anyway you can kill Bloodlord Mandokir, and pray his mount will drop.Same for High Priest Thekal.
Also you could try to get the first weapon set (Thekal's Grasp + Arlokk's Grasp)
wich have a proc that turns you into a tiger for 12 seconds.