Actually, I'd say you have a lot of things going with your current team of 3 hunters. If you could find a dedicated Tank and Healer, you could level really quick in instances. Of course, you personally don't have control over the healer and tank so you can't solo instances, but you could burn through instances like its nothing.

Also, when and if you decide to PVP, you'll tear up other players in this 30-39 and 40-49 brackets without really being a twink.

If you want to solo instances, then yeah, you might have to get two more accounts with the intentions of healing and tanking yourself and slaves.