Hi Nicole,
Nice summary and some great points. One thing to consider (after working in call centers for 20 years) is who/how Widget company came up with the 5 minute average talk time metric. That in itself would be an area of research and analysis. I have encountered several large organizations that had unrealistic expectations of the representative and the duties they perform on that '5 minute' call - especially as new products, functions, edicts and programs kept being added to their duties. Perhaps that talk time needs to be re-evaluated.
Just something to consider in the analysis phase if your very solid steps don't uncover the issue. (Although, as you mentioned, observing and especially interviewing may lead you in this direction. The representatives will not hesitate to tell you what challenges they're facing!).
Thanks for all you do in the community and on your personal blog. I am a follower of both and enjoy your insight and expertise.
Regards.