I'm noticing a huge correlation between invisible walls and Cazadores. It seems to me like someone at Obsidian thought certain areas were too easy to get to for the player, or that they wanted us to take a specific route (the North-Western most Ranger-station), so they just put up invisible routes over all the obvious mountain-routes, and dumped a couple swarms of over-powered super-wasps all around them...so that we get trapped in between an invisible wall and a rock while the Cazadores swarm.
Seriously, did they ever say anything about why the hell they felt this amount of barriers were necessary? I wouldn't even mind having to sneak past the cazadores if I could just go over the rocks uninhibited.
Most mountain ranges and cliffs in the game, like those, are unscaleable. There's always a way to get where you need to go, if you look around. And over them mountains ain't it. I guess they made most mountains into barriers, to make you find the passes or roads that lead to the other side. Sure, they could have made every mountain climbable, but they didn't. :shrug: You can always, um, go around...