No. From my understanding, by design you're not meant to get XP from quests over 6 levels below you. Those will be grey in the quest menu. Quests that are green or within 6 levels to your own, you're meant to get XP.
Therein lies the bug, you can do main quests that are within the proper range, and get no XP. So you should have received XP for a 12 level quest at character level 17.
Hopefully this will be fixed tomorrow, and without introducing more problems. I've held off on main quests all weekend. Pretty annoying, but with everything else there is to do in the game I'm not even close to bored.