Although I agree with what has been said … I think we should be open to trying different things to see what works the best for each of us individually.
* There are many choices for faster than Vo2 work for leg speed
* Even different ways to attack Vo2 max
* I do a fair amount of CV (Critical Velocity) work during base building
* 1/2 marathon Pace
* Some people like doing marathon paced runs – I have come to not value them.
So the concepts are pretty simple – How to best apply them to the individual seems more complex to me.