Grab the old 8-1 seek to work from
Avoid behaviour that doesn't really work.
Run more raycasts so we get things our edge will collide with (rather than just our center). now 1 on 1 collisions are pretty much avoided, group ones.... not so much.
Debug render the avoidance
Use mind reading avoidance (like starcraft 2), makes this almost sort of work.
Increase separation distance. Increase the avoidance steering force based on the distance to collision. This works probably acceptably now.
Only avoid dynamic bodies, flow fields will take care of non-dynamic ones