I use RVO. Agents are not avoiding other agents. I have some characters placed as a line. I expect others to have a path from another side. Their path is through the front characters. Do I have to add a dynamic obstacle on agents?
Local avoidance is, as the name implies, local. So it can try to move to the side of an agent, it is not included in the pathfinding process so the agents will not find a way around to the other side of that cliff.
If you have a stationary agent that you want to act as an obstacle you can add a NavmeshCut to that agent. This only works if that agent is stationary and has pathfinding disabled though, otherwise it will effectively make the ground under itself unwalkable, which will confuse it.