VO2max happens physiologically at about 4k race pace, so you can estimate it with a little slower than 3k race pace.
All this talk about VO2max is false because you can't really do 4k race-pace for 4 x 1600 on the track -- it is too stressful.
Mile repeats are actually supposed to be done at a pace a little faster than LT (15k race pace), and most people's experience will bear this out.
VO2max workouts should be about 2-3.5 minutes for the repeats and matching rest is OK as long as it stays below 3-3.5 minutes.
Something like:
6-8 x 800 in 2:20 / 2:00-2:30 rest -- for a 9:15 3200 runner.
5-6 x 1000 in 2:55 / 2:00-3:00 rest -- for a 9:15 3200 runner.
4-5 x 1200m in 3:30 / 2:30-3:30 rest -- for a 9:15 3200 runner.
Once you get beyond 3.5 min at your current 3-4k race pace that is too stressful to spend 20 minutes at that pace, no matter what the rest.
JK has an excellent explanation of it on this site.
Mile reps are done between VO2max and LT pace (between 5k and 15k pace) -- so that is why the recoveries are shorter (relative to 1:1 recovery).
It is simply because at VO2max effort (MAXIMUM OXYGEN USAGE!) you will be at your max HR by about 25% of the way into the rep and you need about that much time to return to a HR of 120. AT mile rep pace you are below your MAX HR and therefore it takes less time to return to 120.
Try HR intervals ... like 12 x 400 at current mile pace / with a rest long enough to return to 120. 6-8 x 800 works well with this also.
For the 400s take off almost the moment the HR reaches 120 and kind of watch the time ... it should be around 50-70 seconds or your effort is off.
For reps longer than 400, wait until it hits 120 and then wait 10 seconds or so and see where you end up timewise. 1:30 would be pretty short and 2:30 would be getting long.
We used to do these in HS all the time and it was nice because you knew you would be recovered before the next repeat, but you knew it wouldn't be too short. We just focused on running even pace and effort on the reps.