The two better zones for farming are Sholazar and Icecrown:

Sholazar: Accessible at lower levels, tons of nodes, tons of people, quick node re-spawn. Mostly saronite and the odd titanium.

Icecrown: You'd be crazy to do it with a land mount , not so many nodes, so so much people. More rich saronite and more titanium nodes.

Titanium node can spawn pretty much in any saronite (rich or not) node location. Not sure about cobalt node locations.
My favourite place is icecrown. Think about it as a giant horshe shoe - fly where the lower level (where most scourge are) meets the clifs, and you would fly contoring the "horse shoe", rather then just back and forward.

Here is an image that I just did quickly, follow the red path :
[img=http://img70.imageshack.us/img70/7343/icecrownorecl9.th.jpg]