So there is a rune for every dungeon. There is the Rune of the Monk for AC, the Rune of the Nightmare for TA etc. There are three ways of acquiring these runes. When you purchase an exotic dungeon armour piece it comes preset with these runes, you can also buy the runes for dungeon tokens. The third and least reliable way to acquire these runes is to recieve them as an exotic (read: incredibly rare) drop from a chest (possibly mobs?).
There is one big problem with this third method – it’s almost completely pointless because the rune is soul bound. You are going to be able to purchase a full set of runes from the NPC before you will find six runes from drops. If you run the dungeon on several alts, you will more than likely find runes on different characters, resulting in multiple stacks of the exact same rune (because soul bound items can’t be stacked on each other if bound to different characters). Even if you levelled a new toon and didn’t want to buy the dungeon set but wanted the rune set, you won’t be able to use the ones you randomly found in the dungeon because they will be soul bound to characters that will never need them.
So here we have multiple stacks of an exotic drop which will be, in the case of the majority of players, completely useless – and you can’t sell them on the trading post. Why are dungeon runes dropping in these dungeons at all if their poor decisions in their design (soul bound not account bound, can’t be sold) basically resulting in them being completely useless?