Captive Audience (Alliance)

If you can't find captives, head north towards 39, 35. I have only noticed about 7 captives up at any given time when there are a good 20 different runes. Runes containing captives are often found to northern side of the quest area around 39, 35. This is across the other side of the road that divides the quest area. I assume it is because the southern area of the quest zone is much easier to access and avoids the main thoroughfare of horde players so more players start doing the dailies there. If you can't find any captives, head north, often the spawns on north most beaches around 39, 35 are occupied.

I do these dailies using water walking (hunter waterstrider) entering the water at 45, 43 then I ride up to 39, 35. It hits the most commonly occupied spawns for this quest plus you can most of the other PVP dailies and you avoid the horde quest hub.

The runes are in the Dawnseeker Promontory area on the Isle of Thunder ~ Coordinates 38, 38

Runes are red circles on the ground and you need to click on them.
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Empty runes will not count towards the quest, the runes must contain a captive to count. It can be quite annoying as there are sometimes no captives at all.

They tend to be near mana orbs, objective of another quest. Look around for one after you've just busted the other.