You analysis is wrong. The improvement of the best times in long distances (5000 and 10000m) is due to the massive improvement of the organization (private in Kenya, more connected with the Federation in Ethiopia) in the two main African Countries.
In the period 1970-1986, private management didn't exist in Kenya and Ethiopia, and also the occasions for running in meetings with good income were very few. There were other reasons (boycott of Moscow 1980 Olympics for Kenyans, boycott of Montreal 1976 and Los Angeles 1984 for Ethiopians) at the base of a reduced development in those Countries.
During the period between 1970 and 1980, the real occasion for improvement was the Commonwealth Championships 1973 in Christchurch only, when we had the WR of Filbert Bayi in 1500m and a lot of other massive performances.
When you look at the improvement as result of doping, which is your idea about the improvement of 35"8 of the WR of 10000m which Ron Clarke achieved in 1965, without rabbits, on a dirty track, moving from his own 28'15"6 to 27'39"89 ? And, without asking Calculo, how much could be the value of the athletes running in Munich 1972, when Lasse Viren won his first Gold Medal with the WR after falling down, in a race that we can consider tactical ?
Since I had in my career 9 athletes running between 26'30" (Nicholas Kemboi) and 26'55" (Geoffrey Kirui), who never took any supplement (also legal), how can you think the human limits are about 27', at the moment a performance not valid for being in the top 50 all time (so, do you suppose ALL these athletes are doped) ?
You don't have any idea WHAT the real talent is, and WHERE the human limits are. Working with some of them, I can tranquilly say the current WR are, ALL, very much weaker than the possibilities of the same athletes who are the holders.
Rudisha went in a total "solo" in London, and probably could run a little bit faster with somebody pacing till 600m at the same speed that Kipkurgat used in Christchurch 1973 (1'13").
El Guerrouj had a lot of opportunities, for several years, and in the area 1500m/Mile/2000m brought the records at high level, but Asbel Kiprop went very close with less than 50% of the professionalism of the Moroccan, and, if able to stay in an organization as you have in Portland with Nike, or also in some Country with more scientific assistance, could easily run under 3'25".
Kenenisa was not in shape when ran the WR of 10000m, and NEVER prepared the event in specific way. In my opinion, for him at his best running around 26' was not something impossible, and the sane could achieve Nicholas Kemboi is could continue his career after WCh 2005, when he was spiked in the tendon during the race, and never could come back at the same level.
About Shaheen, I was not happy about his WR, that is very far from his value, since in 2006 he was very much stronger than in 2004, but, after failing in Zurich for a problem of pacers, had to finish his career for a stupid accident (his left knee had a strong impact against the door of his car, open, and he needed a surgery after one year of attempts of training again, but also after the surgery he never was able to have more than two following months of training without increasing the pain in the knee again), and his value was well under 7'50".
Don't forget that, when Europe had more interest in long distances, and young talents were not absorbed by other activities, we had runners such as Mamede at the WR with 27'12", Lopes at 27'17" when already 37 and at 2:07:12 in Marathon when 38, Steve Jones at 2:07:13 completely alone after running well under 62:00 the first half in Chicago without rabbit.
Records come when people are interested to organize in the best way one competition, with the best athletes. And, when there are many races paced for the WR, all the athletes of the period can benefit of the pace, and there is a change of mentality at the base of the big general improvement.
We had, in Kenya, many athletes with NORMAL talent who ran under 13' in 5000m during the period 2004-2009. The no. 10 in the world ran 12:54.99 in 5000m in 2003 because of the races of Haile and Kenenisa for trying the records, and 27:00.30 in 10000 in 2007 because the organizers looked at good races with the aim of WR. The year with the best level for the 10th in the World in 1500m was in 2015 (3:30.29), well after the adoption of the Biological Passport, so all the elucubrations about the fact that the performances are slowing down because the BP are bullshits.
I don't deny somebody could have taken EPO in the period 1990-2005, I deny this can be considered the COMMON DENOMINATOR of the improvement. Haile Gebrselassie, in spite of what the most part of Letsrun readers suppose, NEVER HAD Hct HIGHER THAN 43 WHEN IN TOP SHAPE, and all the ideas about EPO are ridiculous.
The reality is that, sometimes, we have among talents somebody that is a SPECIAL CASE. This was the case of Usain Bolt, of Edwin Moses, of Jim Ryun, of Michael Johnson, of Sergey Bubka, of Hail Gebrselassie, of Kenenisa Bekele, of Stephen Cherono, of David Rudisha. These were athletes NOT BEATABLE at their best, because they had something MORE than the other best talents in the same events.
If you have the opportunity, and the fortune, to coach some athletes like these, your idea about human limits changes, and also your idea about the percentage of intervention of any kind of doping in their performances.
And, about the blood doping, you can learn that EVERYTHING YOU TAKE FOR ENHANCING YOUR BLOOD VALUES AT THE END HAVE THE OPPOSITE EFFECT, BECOMING A LIMIT FOR THE BEST POSSIBLE PERFORMANCE.
We have top athletes in the same events reaching their best with Hct under 40 (the case of Bordin in OG 1988, or Christopher Koskei winning Gold medal in WCh 1999) and with Hct over 52 (natural, like the Italian Genny Di Napoli national record holder of 1500m). I have now, among my best athletes, somebody with 53 of Hct and almost 150 off score, and somebody else with 40.5 and 13.5 Hb, and these are their natural values. And, in any case, don't forget that for EVRYBODY of these athletes, when they reach their best shape, THEIR VALUES BECOME LOWER. This is the trend, if you want to attack some record on the track, and not the record of the higher Hct, that in the common events doesn't exist.