I have to add here that since my last post a Greek scholar friend has informed me that he thinks the GS rule may sometimes apply to the plural, in particular in Eph. 4:11. So there is not a total consensus among Greek scholars.
A basic statement of the GS rule is that if there are two singular nouns describing a person or persons connected with kai ("and"), with a definite article before the first and not the second, the two nouns are referring to the same person. I'll not derail the thread by giving the technical points made by my friend to say that applying the GS rule to plural nouns is possible. Suffice it to say that there are some out there who agree with MacArthur. My objection to the examples given by my friend (Jn 7:45, Mt 2:4, Mt 4:25, Acts 1:8), are that they refer to two groups or locales being treated as one, but MacArthur's position is that pastor-teacher is one office, not two being treated as one.
My original advice to study the Greek still stands. As a preacher friend recently said to me, to him reading the Bible in English is reading it in black and white, while reading it in Greek is like reading it in color. :type: