That's hard to tell because the damage output had a really big variation caused by the 3 attributes body, mind and focus. The LvL didn't affect it that much.
My lvl 28 Runemage dealt more damage than some other lvl 50 runemages because I pushed my mind attributes alot and combined some skills together to reach a damage amount of 7k with the finisher.
The average damage from that mage was around 800-1500.

But its too long ago to tell specific numbers. You could watch some of my videos to see what damage I dealt on different levels and how much for example the "Setup" skill affected the output.
But that would be only for Wrathguards.

The damage output overall was very different from classes to classes.