I found an absolute treasure trove of Aspect Runes the other night (don't get too excited, they were still almost all Ta).
I just hit V14 and made myself some armor and I'm looking all spiffy. I decided to go get my Cyrodiil skyshards and try to complete the delves while I am at it. I picked a 30 day "dead" Cyrodiil campaign where EP has the map totally dominated. Place is empty. As I began doing the delves to get to the skyshard I noticed that each delve had 2-4 Aspect Rune in it. No Potency Runes, No Essence Runes. All Aspect. Additionally if some respawned on my way out of the delve, they were also aspect runes. This was really weird and happened in at least 6 different delves. I drove my guild crazy that night talking about it I'm sure.
Did another couple delves the next day and it also had ONLY aspect runes.
My only thought is that everyone scoured above-ground for runes, pushing all the spawn points underground. Why they were all aspect I have no idea.