I've become used to the usual manner of daily reset where you collect a quest, and if you don't do it on that day, you can still turn it in before the quest resets on the next day, and still pick up the next day's quest which has accumulated. This applies to practically all the dailies I know - Undaunted, crafting, world bosses etc.
However the Tho'at daily in IA seems to work differently where there is no quest accumulation, and if you're late turning in the quest, you basically just waste a day and have to wait for the next reset to pick up the next quest.
Is this a bug or intended? Is it not supposed to be a daily?