I don't agree. The wheel on the new Tx has good speed control. If you move the wheel just a little, the camera will tilt up or down very slowly. Moving the wheel further increases the speed.
But OP referred to "pan speed". Do you mean moving the camera to left and right, or up and down? Moving it to left and right is done by the Phantom's yaw, which I agree takes quite a bit of practice to move very slowly.
Perhaps others have ideas about slowing down the yaw, if that is your meaning of pan. The yaw sensitivity may be able to be adjusted in the Phantom Assistant or RC assistant.