Jew on, I think the long tempo run is CRUCIAL, but it sort of depends on what you mean by "tempo". I think 3 runs at goal MP, 10, 12 and 14 miles, in the middle of a long run (20-22 miles) is necessary. Each time you do this, the pace never varies. What does vary is the distance. They should be done every other week, in my opinion, and stopped about a month out from your goal race.
Running 10 miles at half marathon pace is probably not worth it. However, several 5-7 milers at half marathon pace, I think, has their place. I do a bunch of 5-7 milers at 1/2 MP early in my training cycle and then transition to MP stuff about 2 months out from my taper. I still go 1/2 MP, 10k pace, etc during those last 2 months, but most of my work is either aerobic running or at MP.
BB, when I started up again in 2009, I figured I needed a goal for a race I never ran before, because otherwise I would be disappointed with my times. Being around the NYC Marathon for the last 13 years, that became an obvious choice. I also figured if I wanted to race short again (3k-10k) that I needed a real base, and the only way I could get myself to do that was to train for a marathon.
You know, with Mcmillan its all relative. You can't take your PRs and compare that way. For example, I think I'll probably be in 16:00 road 5k shape this winter/spring leading up to Boston. Mcmillan has that as a 26:31 8K, 33:14 10k, 1:13:58 1/2 and 2:36 marathon.
That all sounds about right for me. If I run 26:50 for 8k in Central Park leading up to Boston, I'll be confident in my 2:37-39 goal... so that all sounds good.
BUT, I guarantee you, that when I was a 4:37 miler in hs (junior year) I couldn't run 2:36 for the marathon or 1:14 for the half or 33:00 for a 10k. But I could run 2:00 in thee 800 and 52 in a 400.
So I think it depends on where you are with your running and what kind of training you did to get there. Coming from marathon training, all the times seem about right. Coming from 800 or mile training, nothing after 5k sounds right!