Rolled Pirate Booty twice for 150 gems and got just lowest grade experience books and in same minute rolled once Thunder prize, and gave me same experience books.
[edited by Cichociemiak]
This is not bug, and it should not be considered as bug. It is all random, you can get good prizes, and other time you will receive not very good prizes. Yet it is not reason to use offensive words, since this is only game. Most of ppl didn't get any good things from Pirate Booty, i also tried some time ago, rolled few thousands of gems, and didn't even received single reward from third grade. That's why i am not participating this event other than free entry. I prefer to try mu luck when Hero Collector is live.