The kinematic object manager will be able to be switched to Update in version 2.2 so that will help there, but unfortunately there isn't much that can be done for OnAnimatorMove right now. This is a situation where the job system will really shine. I have plans to switch to this but it'll take some time.
For right now you have a few options:
1. Disable horizontal/vertical collision detection for your AI. With a NavMeshAgent you'll likely be able to disable horizontal collisions, but will likely need vertical collisions.
2. Remove any abilities that you don't need.
3. Disable IK to see the performance differences.
4. Try turning on Auto Sync Transforms on the Kinematic Object Manager. This may lead to worse performance but it's worth a try.
5. Depending on the complexity of your AI, you may be able to not use the character controller at all and go with your own solution with just BD and the navmesh.