Heh, technically you do kind of level an alt - and this is where I say it's very similar to FFXI jobs - each class earns xp and skill points independently of the other. You cannot level them simultaneously, which you do in GW, as memory serves. So you spend twice as long on one character, but the nice thing is that it gives you time to work on tradeskills, etc. equally across both which is a fairly involved and time-consuming process. It works out nicely in terms of what you can do along-side dual classing in how it plays out in RoM.