Here is a good mod if you using any, I found it a bit rushed having to be within 5 levels to maintain some experience from the quests. There is different settings, I used mixed, 100% for Quests as normal, but if they greyed out on me I got 50% at least. But as you can see, there is 4 more settings to pick from.
Always Full Exp by Toommy1984
Also, if you have the DLC's and doing them after main quest. You might want to do some of those treasure marks (underwater question marks), since you get a nice haul from them and earn coins too.