When I try to add 2 copies of Queen Anaru to my deck i get the following message : "The specified champion belongs to the Queen Anaru Rune Group of which you already have the maximum allowable 1 in your battlegroup." I can't see the reason to why this is limited to 1. I can add 2 copies of other legendaries and she isn't labeled as a hero. Additionally, I have played with both copies in the past.
Some runes were recently changed to be limited to 1x in a BG, such as Coragh and Anaru. This is part of a larger change to a set of runes. You can find information on this on the back of a rune on the lower half. There should be a line that says "Deck Limit: x."
iirc, she had an ability on release that, if you deployed 2 of her, would explode them both. they removed that ability when they changed the deck limiter around i think, but in general named runes (like heroes or ambassadors or so on) are more likely to be unique i think
