I´m not sure but it won´t surprise me if Kirkland was Red John. People say he can´t because it´s too obvious. What if the writers are making Bob look too obvious so people think he is not Red John but he really is? You know, hiding a truth inside a truth so it can look like a lie. Also, Bruno Heller said we will be dissappointed to know who Red John is. If Bob Kirkland really is Red John people will be dissappointed because it was very obvious. 
I don´t really think it´s him, I think Kirkland is looking for revenge against RJ or he works for him, but  I can smell the trick that the writers are playing.