Dunno if this is a bug or not, but reporting it anyway. I'll load it to the bug tool after I'm done here.
Joined someone doing Dreaming Dark three times so that they could get the ioun stone as an end reward. They had to go to lunch after the first completion, so I finished the next run solo, casual, no problem.
The toon I was using had done the Dreaming Dark once before, so those two runs plus the first one meant that he'd done three by my math. Sure enough, there was a blue ioun stone in the end reward list. Didn't pick it, for obvious reasons. Then decided to run DD again, for LOLs. Okay, I don't know why I decided to run it one more time. But I did. See here for my end-reward this time:
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Note that I've completed DD 3 times (was 4 after I picked my reward).
So either a) I should have bought several lottery tickets instead of running DD or b) something fishy is going on.
Going to run one more time to see what happens and then load up the bug report tool.
Edit: fifth completion had normal reward