Warding the Walls

This is one of the four Elemental Dailies offered by NPCs in either the keep or the base camp when the battle is NOT active. These dailies involve you collecting 10 items from elementals or players in a certain area of Wintergrasp. Lesser elementals (both factions can see them, have about 13k HP) have a very small chance (About 10%) to drop 1 item. Revenants (Only the Controlling side can see them, about 25k HP) have a small chance (about 20%) to drop 2 items at once. Any enemy player that is killed and looted in the DESIGNATED AREA will have a 100% chance to drop 1 item. Note that only the

As of May 4, 2009:
While in control of WG and no battle going on, I had a 100% drop rate from Glacial Spirits and Water Revenants.
Coords are: 37,37 to 37,55.

The breastplates can drop from Water Revenants and Glacial Spirits. They do drop if you're in a raid, and they drop from Water Revenants and Glacial Spirits outside the Glacial Falls, too, unlike what the quest implies. I'm not sure about the dropping from Alliance part.

Also, they do drop at all times - not only when a battle is on. The drop rate is really bad, though, so don't be discouraged if one doesn't drop for a while.