Bâr Húrin is a settlement located within the area of South Ithilien in Eastern Gondor - 73.2s, 12.3w..
The Bounty Board is at 73.4s, 12.9w
The 4 Bounty Posters are Langarch, Maeganc, Ronkurz, Yambahul ..
The Locations do not show up on your map so here are the 4 locations to help find these 4 mobs..
1) Langarch ( Boar ) 72.9w, 14.2s - just west of Bar Hurin
2) Maeganc ( Bear ) 77.8w, 17.7s - walks in the cliff area
3) Ronkurz ( Troll ) 68.6w, 8.1s - He is in a small camp site. Sometimes he doesn't respawn for a long time and other times I have seen him respawn in 1 min.. If he isn't there just come back in a few.. One time I left, killed Yambahal and returned 20mins later and he was there..
4) Yambahul ( Orc ) 73.6w, 7.8s - He is inside a tent most times at the very top of a orc camp.. I believe there are 3 levels to this camp, just go to the highest tent area.. One time he was walking around the tent but every other time he was inside..