I played UB for quite some time, but I have a tank and a healer in my setup! :P
UB was really smooth runs (besides the last boss) and actually yielded lots of cash (mining, skinning, herbalism and all those 600 Sanguine Hibiscus that sold for 4g each on average).

With or without tank+healer I think UB might be a rather rewarding instance at your level.
Mana-tombs will just get you frustrated with the aoe-fears (since you will tank them within melee range to your entire group :P)