Colliders and Astar

Hello, I am using Aron Granbergs A* Pathfinding system in my FPS game. I am making a zombie type of game so it works out quite well. each zombie has a Character Controller, as well as the player. After doing some research I found that OnControllerColliderHit doesn't work with two character controllers. I also found out that many character controllers can cause slowdown and lag. So I tried using a capsule collider and rigidbody on the zombies. So now OnControllerColliderHit works (to a degree, but the bad thing is the player has to be moving for the zombies to hurt him). and OnCollisionEnter yields no result. This wouldn't be that big of a deal, execpt that now the A* is all messed up. The Zombies get stuck often and dont move, although debugging shows the path towards the player. The zombies slip,slide,and glitch often, and Most Importantly they move uphill with difficulty (If at all). So I am stuck with a serious dilemna.

--Use Character Controllers. Perfect Pathfinding, but no Collision Detection with player. Slower Framerate

--Use RigidBody and Capsule Colliders. Bad Pathfinding and Bad Movement, and decent Collision Detection Faster framerate

There must be something I can do! I have tried adding a capsule collider along with a character controller, but the movement is jittery and (please correct me if I am wrong) but the character controller physics are still calculated, which causes slowdown yes?