I love how many secondary quests in this game involve killing a group of bandits and then finding a letter on one of them that's basically like "I've almost stolen enough money to save the orphanage / pay for my mother's life saving surgery!" I feel guilty but not guilty enough to reload my game.
Also the XP bug went away on one of my saves and I've been able to progress again! My advice to people effected by it is to see if you have a lot of grey low level quests in your queue, and clear out a few. Then progress the main story a bit... after a couple story quests, experience kicked in again, and I even got delayed experience from a story quest that hadn't given me any. It seems especially bad in Novigrad where Main and Secondary quests overlap quite a bit but have varied recommended level requirements. I think if you get assigned a secondary quest via the main question but are over leveled for the former, it bugs out experience on the main quest.