The slowness might not be related with the supplicant side only, but with the authenticator side too. You should check the 802.1X quiet-period which is 60 seconds by default and basicallty dictates "how much time the switch will wait after the EAP-request-identity frame is sended from the switch/authenticator side, after the supplicant gave the incorrect authentication information), and the transmition timeout which is how much time the switch/authenticator will wait in order to send the EAP-identity-request to the supplicant. If the supplicant doesn't respond the the EAP-request-identity frame this is the timeout that applies and not the quiet timeout.
This information should be synchronized from the supplicant and authenticatior perspective. With the CSSC client is very easy to do so.