its hard to reply on ur question . i would need to know if ur queued as a DD or tank ? or was it after midnight? or during the afternoon?
after midnight it will always take longer , also there will be always more DD's then tanks. IT was the same with 2.0
i can only speak from my own experience i had in game so far , the only times it took really long for a dungeon to pop was when i lvled a DD class after midnight :P