Lately, I've been getting queued into the same heroic dungeon multiple times per day through the Random Heroic system.
If this is not a bug and is working as intended, then I would like to suggest the following:
The system should be adjusted so that it first prioritizes dungeons for which the player does not already have a lockout (ID). Only after all available "free" dungeons have been exhausted should it start offering dungeons where the player already has an ID.
If this is a bug, then it should be fixed. Today I completed around 10 Random Heroic dungeons and was assigned to Pit of Saron twice and Halls of Reflection twice, even though several other heroic dungeons for which I did not have an ID were still available.
I'd also prefer not to get the same dungeon(s) several times out of, let's say, 10 RDF HC runs. It would be neat, if possible, the same dungeon couldn't come again until few other RDF's are completed. Just my two cents. Oh, and I know, it's random RDF, so I don't really expect it to change, but one can dream.
I'm not sure whether it's working correctly. Yes, I understand that it's a random HC, but it wouldn't be a bad idea to implement a priority system where a dungeon for which the player does not yet have an ID is given higher priority than one for which they already have an ID. Otherwise, it can happen that you get the same dungeon three times in a row. Yesterday, I ended up doing the same dungeon twice consecutively.
(It can even be exploited if players from your guild queue for a specific dungeon and you simply join through Random HC.)