Quests in the Gravenwood  

If you follow the epic story line and do all the quests along the way, you still are only at about 19/24 for this deed (unfortunately, the five Tasks on the Task board at the Rohirrim Scout-camp do not count toward this Deed).

I found the last 5 quests at two separate NPCs who were pretty well hidden.

The first was Cuthric at 79.7, 13.0. He had three quests which take you into Rhuvel-cadlus at 80.1, 13.4.

The other NPC is at 84.3, 11.6. I do not remember his name, but he also has three quests which take you into Ak-ghru at 84.6, 10.7.

Hope this helps you get your Deed!