On live server.
You have to be a mage unfourtunatley because blink is required(but i do not know for sure because i have not tested it with other classes)
I attempted to keep the guide simple but i'll try to answer questions so here we go
Go to where Arthas and his men are(you don't have to even do the chromie quest)
Jump into the water and head towards the invisible barrier(red arrow)
BTW all the COT instances have a very thick "fog of war" effect when you attempt to leave the area so don't get discouraged by it
When you hit the barrier get about this far under the water and face the barrier then BLINK!(if it does work the first time just move a lil bit and try it again)
Other side of the barrier under the water
SUCCESS!
For navigating this region, use your minimap, use EPL map as a reference because it is nearly the same region(approxitmately the top left corner chunk of the EPL map ending at the troll area horizontally and the bridge and long ditch vertically.)
This is a little broken village at the end of the path according to your minimap!
Points of interest include the camp and GY south of where naxx used to be. UD troll camp to the north east. The towers for the pvp in EPL. The portal to blood elf capital. backdoor to ud strat. and a drop off in the northeastern and southwestern corners of the "instance" that will drop down to the blank area where my first screenshots were!
ENJOY!