If it helps support your cause, 3 x 400m at 800m pace with about a 4 minute jog between reps is a very common workout I prescribe for 800m runners as they close in on their peak race. I find it highly effective!
i'll be doing some time trials soon. they are called 800m races, to end off the season, and i hope to change my letsrun handle then. :) why is the 600 tt the way to go? 3x400 is the plan. i'll save the 'one timer' for the races, or else i risk racing too much. now you are going to get me started on the lydiard time trial concept....oh no.....
Tinman, I think you gave coach Kvalheim a appropriate advise of changing recovery jog of, what's her name, Suzanne?, from 100m to 200m (when performing 200m repeats). I think she would be much better off doing them that way. Arthur would have been proud.