A high enough e boost can solve any energy issue. I never used a sigil til 170, thanks to e boost. Could have never used em but i had them laying around.... So i think you could get to any lv without a sigil if you use e boostI've played mage and rogue enough to know I like mage just a little bit more. But with its energy problems and such, I dont know what to choose. Plus I dont have sigils so I dont even know if I can be a good dps mage in long fights even with e boost.
If you need help with mage, i have a guide on the mage forums for an ice mage if you want to check it out. If you want to be fire, just replace the ice stuff in my guide with its fire equivalent.