Speaking / listening assessment strategies

Today is the first time I'll assess speaking and listening as part of a larger summative assessment.  Already, I can see that the rubric by trimesters that I gave the students will be insufficient to the task of assessing their conversation accurately in this context.  The fundamental conflict is that the assessment task doesn't reflect the grading scale, and the grading scale doesn't accurately reflect the learning objectives. 

I remember that creating the comprehension rubrics were particularly difficult; I may need to revisit them in light of these difficulties.  More clarity when I'm not actually at school.