The power of divided labor.
The first time I was asked to teach with a partner was as a full-time proselytizing missionary. It worked out well, but I thought little about it as a practice. Later I was asked to teach a Sunday School class with a partner and found the process nearly impossible. But recently I have found it my preferred technique for teaching computer science.
The key, I have found, to good paired instruction is to not overly separate the portion of the lesson each presents. I have spoken earlier about the value of listening as an educator. It is, frankly, difficult to listen and speak at the same time. But with two instructors, one is speaking at a time, leaving the other free to listen to the students. When the listener recognizes signs of misunderstanding the roles can be reversed on the fly.
I have tried this technique several times with various classes and found it to go over very well. I suspect that there would be significant advantage if every dissemination course Not all courses are about disseminating information; this is usually reserved for courses laying the foundation of a field. were taught by a pair of instructors, at least one of which was skilled at listening to groups. I also expect that such a model would be a very hard sell to educators.