I am currently working with hundreds of AI that follow the character. The problem is that the AI tend to get stuck on each other. If I change the AI capsule size to be a radius of something like 2 or 3, this fixes them getting stuck, but they no longer seem to run in a group, as they are all pretty much overlapping. I want them to be slightly spread out, but not get stuck on each other, has anyone dealt with something like this before?
Maybe look into some formation system like used in Warcraft 3?
I think the behaviour you’re looking for is called ‘flocking’. ‘Boids’ is one example of how to move a large number of entities without them crashing into another. Here’s a processing example.
Look into RVO collision avoidance. I’d give a more detailed response but I’m on my phone out of town 
it should be located somewhere in the character movement settings. Just enable and then set the radius.
I have turned on avoidance, and messed around with various settings for my AI character, but they don’t seem to behave any differently.