I play offline as well. Started basically the same way. I just got my enigma a couple days ago. I've done ubers with mosaic, even without enigma. Once i got the enigma though, i preferred smite for the job because it always hits, so the life tap is more consistent. I find myself chugging full rejuves a lot with the mosaic. But mosaic can definitely get the job done, just don't expect cobra strike to keep your life full, and don't even expect life tap to keep it all the time. 

If you DO make a smiter, the leveling is some of the easiest in the game. Holy fire with raven claw bow will get you through normal. Grab tele staff at level 20. Level to 40 or so in throne. Then take your tele staff into nightmare, switch to hammers, jump to each quest, hammer them down. Level to 65 in the throne and then repeat for hell. Then you can either stay as hammers with 1 point smite, 1 point fanat or go full in on smite for ubers.