This is a warning for anyone who thought like I did that it would be clever to just do the mainline story quests (the ones with a shield ! icon) and save the side quests for later. Well, guess what, you'll hit a wall at level 57 where you can't continue with the mainline story quest chain until you get to 58.
So, time to re-trace my steps and start grinding side quests for 3/4 of a level.
Thanks O'Blizzard!