Well, you can try this: On the Carbonite Quest Watch (quest tracker) header (the part with the colored buttons) there are two "arrows" on the left side. Click the second one (if you hover it the tool tip will say "Priorities").
This one: (Please click the images for a larger version. Might open in a new browser tab or window.)
You can try adjusting the two quest giver level sliders in that menu.
There is also a quest giver level option on the "Quest" page of Carbonites options, but I am unsure of exactly what it (or any of them, really, since i don't mess with them) does.
I hope this helps you with your problem.