They are too short I feel. Which is a shame because the game is huge >.>
The youtube videos unfortunately do not include all of the romance content in the game. All of them seem to end after the "final" scene, whether that be the sex scene for Cass or the couch scene with Josie. There is plenty more romance content peppered throughout the game after that in the form of dialogue at skyhold, or in story specific areas. (i.e. Winter Palace) A lot of subtle changes too that add to it. Then there's the romance content at the end of the game from before you hit the arbor wilds, to walking down the steps at Haven, to the interactions/cinematics at Skyhold.
The romances were definitely not short if you take into account everything in the game that relates to the romance. Like I said the sex/couch scene isn't the end. Bioware did a good job with making it progress through the entire story with this game. Gave it a nice flow.