The biters seem to have gone to the school of Attacking One At A Time, at least when large groups attack.
[Edit] The server seems to be unable to attach my save file and video of the issue at this time; I've uploaded the video at https://youtu.be/MMcTEQN-lDc
Basically the biters collide with one another and mill about in confusion until enough get killed off that they can all rush the wall at once. It's helpful for me, but I don't know that this is intended behavior. I did have to significantly upgrade my defenses with 0.17 so there is a definite improvement over 0.16.
[Oxyd] [0.17.7] Biters behaving badly?
Re: [Oxyd] [0.17.7] Biters behaving badly?
Thanks, should be fixed in 0.17.70.