I also am having this problem.
Ipad air 2.
First, I did quests with just priest and rogue and can't remember having any problems.
I bought the bundle and added 4 other new characters to my level 6 priest and rogue. No one got their level rewards.
I deleted everyone and just did a quest with priest rogue and wizard. No one got level rewards. Deleted them, tried again with same configuration. Theyou different that time. Played again with those characters and they did not get thier level 6 rewards.
Guess I'll wait and hope this is fixed soon. Not getting the level rewards takes a lot of the fun out.