first you need something you can use to survive a normally fatal fall. Something like a rogue's safe fall will work.
this uses the supply crate exploit in stratholme - open supply crates in stratholme opens gates in stratholme.
so
1: go to stratholme (not the one in CoT) and use the supply crates to get to the last area with the slaughterhouse
2: to your left, you will see a passageway going out blocked by series of gates.
3: now open crates until the gates disappear to the raid portal (a friend is useful). opening a lot of crates is important if you're alone as you could be stuck between the portal and the next gate.
ttp://img8.imageshack.us/img8/3271/entrancestratraid.jpg [add h to ttp]
ttp://img24.imageshack.us/img24/1705/entranceish.jpg [add h to ttp]
4: to get through the raid portal, get some gargoyles patting around the area before aboms (get rockwing screechers not the rockwing gargoyle ones), pull them to the raid portal and wait for them to use fear on you.
ttp://img9.imageshack.us/img9/6821/stratpastraidportal.jpg [add h to ttp]
5: after you get through the portal, if you opened enough supply crates you will be able to see the end of the passageway without gates blocking it. then you can use whatever you brought to prevent your fall death and jump off.
6: there will be a huge area where you land and when you look above, you can see stratholme from below
ttp://img8.imageshack.us/img8/1313/understratholme2.jpg [add h to ttp]
edit: added more pics