The mesa snakes are to the NE of the zone in from Blightfire, not to the NW with the bears and wolves you kill for the other hand in quests for Madu. I killed what felt like a bajillion diamondback snakes thinking it just had to be a snake... in the mesa....
These snakes do add, but they seem to have a very short assist range. I was kiting one with my bard alt and had another join in when the one I was killing ran almost over top the add.
These snakes do not add when attacked, so they are easy to solo. While trying to snare and DoT one of them, another popped right on top of my pet and the snake I was attacking, and didn't attack at all... whether this is just luck or not I'm not sure, but it was there for a good two seconds, which is plenty of time to aggro.
basically directly north from zone in from blightfire. If you go to Scout Madu, and turn north, you will see a river, with a bridge crossing it. If you cross the bridge, going west to east, you will see a path that will lead you right to them.
____________________________
Urnihixul Noctumbra
~Order of Seibwen/Ancient Fellowship/In Via Damnum/Alliance of Hope~ 108 Rogue