I definitely agree with the above posters. The exact paces I proposed based on race distances, etc are fine for guidelines but in reality, the "art" of training is to be able to feel those paces naturally rather than be restricted to looking at your watch.
Malmo put it best I think - you should know what easy, moderate and hard paces feel like just like you should know what tired and hungry feel like. Just listen to the feedback your body is providing - it's the most advanced piece of running equipment you own.
For myself I think what I used to deem as easy pace was actually not that at all - I never used to finish easy runs feeling refreshed, recharged, ready for more, etc (how I think you should feel). Now I've slowed down on the easy runs, run more and do so more consistently because of it. What easy pace actually is varies with what I did the previous day, how much sleep I got, how many beers I had last night, etc. The actual pace is just a secondary piece of information about where you are at. It's certainly useful to look at sometimes but ultimately getting the feel for what an easy run should be is far more important.
I also think the "comfortably hard" effort I run now is slower than what I used to think that meant. Contrast Malmo's idea of what a tempo run should be (somewhere between M pace and HM pace) to what many people describe as such and you'll see a huge difference.
All this isn't meant to make you believe that all your mileage is being run too hard - more to take a different perspective. Think in terms of the feeling of easy, moderate and hard instead of (insert pace here) or fast and slow.
This is a serious divergence from the topic of aerobic development, LT, etc but it's still good stuff.
BTW - HRE, those extreme examples of aerobic monsters you mentioned are incredible. That's hard for me to fathom.