I've leveled a necro to 50 with a lot of soloing, very easy on this server.
On live i leveled a wizzy to 65 on live, quadding is hella fun but way easier with jboots and tstaff.
Buddy of mine also leveled a mage to 65 with a lot of soloing.
Bards swarm kiting is sexy, and shammys are incredible at soloing too.
Really just find something you like and honestly you can find places to solo, there are a lot of guides on the wiki that will help you figure out where to go.
http://wiki.project1999.com/Players:Adventure look at the guides tab on the left
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