I'm wondering who the betrayal refers to, particularly. My gut instinct would be us, the Scions, but I would hardly consider the Syndicate to be "loyal" to us in any way, and "hands" implies someone who aids or aided us. I also hesitate to consider it as Raubahn and Nanamo for the same reason, although Nanamo's maid would certainly be considered loyal. That pretty much leaves Ishgard and the Dravanians, so it seems like they may not have been enemies at first, as being betrayed would have implied, if not friendship, a mutual understanding between one another.
But the problem I find is that the phrases "souls point/march Heavensward" and "evers rings out our song" point to two different 'voices', if you will. The former is Ishgardian, as they view Halone's Hall as being among the heavens, the latter definitely sounds Dravanian with the use of "song". So, does this song refer to them both, such as the line "Bound fast unto our fate", speaking of how they are, or were, destined to war amongst one another? I really do wonder what the other lyrics are...