The theme you hear at the very beginning of the video has been present in the OST since the one that was leaked during the Alpha. However, the version you hear during battle definitely isn't present in that set, and it seems to be a variation on the main exploration theme in that dungeon.
Also, to put hopes up some more for differing music etc if you listen to the Auto-attack video, you will notice that the theme that plays before and after he is fighting the Goblins to show off the auto attack, that the field music isn't the same as we currently have in La Noscea, so it seems they are diversifying the music as a whole, which bodes well for dungeons.
I really enjoy the music in this game, so I do hope for more (like getting all the music from the alpha used outside of short cutscenes! *grins*) as well as all new stuff for future content.