I don't want to contest your theory. Nobody can be sure about the fact if an athlete is clean or not, exactly like nobo0dy can be sure that you are not a thief. I want only to remind that YOU MUST PROVE TO BE INNOCENT WHEN ACCUSED, but without any accusation, is the PROSECUTOR that has to prove he is guilty.
Anyway, that's not the point.
I want only explain several other reasons, because the most important density of results is in the period 95-01.
1) In every event, and in every sport, there are cycles. Sometimes we have extra-class athelets, sometimes not. We are still speaking about Coppi and Merckx in cycling, about Mohamad Ali and Sugar Robinson in boxing, about Bjorn Daehli in cross skiing. Who was the number one ? There are speculations about it, but NEVER is possible to have a clear and objective answer. The history of T & F is full of athletes able to overtake the mental limits of the moment : look at the chronology of WR.
100m : 37 years for an improvement of 0.16 (from 9.95 of Hines in altitude (OG in Mexixo '88) to Maurice Green 9.79 in 1999, remaining till 2005 - and 5 years (including 2010) for improving of 0.21 (till Bolt 9.58)
200m : 11 years for moving from 19.83 (Tommie Smith, 68) to 19.72 (Pietro Mennea, 79) with 0.11 of improvement - 17 years for improving, thru 2 different races, of 0.40 (Michael Johnson, 19.66 and 19.32 in 1996) -
400m : 20 years for improvement of 0.57 (Lee Evans, 43.86 in '68, to Butch Reynolds, 43.29 in '88, still 2nd performace all time 22 years later)
800m : From Wooderson (1:48.4 in '38) a big jump to Rudolf Harbig (1:46.6, increasing of 1.8, in '39). From Harbig, 16 years till Rogers Moen (1:45.7 in '55) for an improvement of 0.9. In one solution, improvement of 1.4 from Peter Snell ('62), and after this 17 years with an improvement of 0.9 only (Juantorena 1:43.4, till '79).
1500m : A period lasting 14 years (from '43 with Haegg, Strand and Lueg at 3:43.0 till Salsola and Salonen 3:40.2 in '57) with an improvement of 2.8. In one year, improvement of 4.2 due to the phenomen Herbert Elliot (3:36.0 when was 20y). Other exceptional jump with Jim Ryun (2.5 in one competition, from 3:35.6 till 3:33.1 when was 20), with the first runners under 3:30 in 1985 (already EPO ?). Who knows athletics, knows that Elliot and Ryun were athletes of unbelievable potential, ending their career very early, because at that time T & F was not professional. The same athletes, in the athletics of today, can last 10 years more, running 5-7 seconds faster (and don't forget that rabbits were not allowed).
3000m : Kip Keino was able to better the WR of 6.4 running 7:39.6 in '65, exactly 22 days after the WR of Siegfried Herrman (7:46.0), that improved the WR of Michel Jazy (7:49.0) after 43 days only. So, in the period of about 2 months, the WR moved from 7:49.2 to 7:39.6, bettered 3 times by 3 different athletes. The improvement of Komen (from 7:25.11 to 7:20.67) has about the same coefficient of improvement (also if I accept the idea that, for this type of distances, EPO can work : look at all the ER of Mourhit, 7:26.62, 12:49.71 and 26:52.30, and his victories in WCCCh, CASUALLY BEATING KENYANS (somebody can suppose the talent of Mourhit was the same of the Kenyans he beated ?).
5000m : In the period '54 - '57 there was an improvement of 22" (from 13:57.2 of Zatopek '54 till 13:35.0 of Vladimir Kuts in a "solo" in Rome '57), with 5 different runners : Zatopek, Kuts, Chataway, Iharos and Pirie. After, there was the period of Ron Clarke and Keino in '65 : with 4 records in the season, they increased of 10"8 (from 13'35" to 13'24"2). And, after this, directly Clarke improved of 7"6 next year, running 13'16"6. We needed to wait 12 years for the same improvement (Rono 13'08"4 in '78), and after this, in 17 years (till '95), several athletes (Moorcroft, Aouita twice, Gebrselassie and Kiptanui) had the same improvement (till 12'55"30). Immediately after the WCh of Goteborg, Gebre had an unbelievable jump : 12'44"39 (almost 11" better than Kiptanui) in Zurich. The question is : having run 12'56"96 on 4th of June and 12'44"39 on 16th of August, he was under EPO the second time only ?
400 HS : What about Edwin Moses ? Do you think was doped, or SIMPLY WAS A PHENOMEN not only as talent, but as organiser of his life looking for athletics ?
POLE : What about Bubka ? Was the only doped (looking at the difference between him and all the others), or he had different specific talent ?
LONG : What about Beamon (improvement in one competition from 8.35 to 8.90, 55cm) ?
So, we need to accept that athletes like Gebre and Bekele, like El Guerrouj and Komen, like Michael Johnson and Bolt, like Bubka and Zelezny, like Al Oerter and Daley Thompson, cannot born every year, and, when they go to athletics with full focus and good training, can give their print to long period of activity.
2) The problem of rabbits. I have a direct experience about it, because, for the period of 3 years (2004-05-06) with Shaheen, ALL THE ORGANISERS ASKED US TO TRY THE WR (also when the shape was only 80%) giving the best rabbits possible for this attempt. Rabbits are too much important when you look for a WR. For example, the shape of Shaheen in 2006 (in Zurich) was very much better than when he beated the WR in 2004 in Bruxelles, but the rabbits were no more of the same level. During 2004 and 2005, there were professional rabbits (the French Le Dauphine as first, sometimes Vroemen of Luis Miguel Martin as second) able running about 8'05" maintaining a very even pace, and Shaheen needed it till 1800m (never they arrived till 2000m in front). In 2006 all these athletes disappeared or lost their shape (in Bruxelles 2006, we knew 30' before the meeting that the rabbits were not ready).
In the period '92-'02, there were rabbits absolutely perfects : William Tanui (previously Olympic Champion of 800m !) for 1500m (El Guerrouj needed 2'46" - 2'47" for the first 1200m), Martin Keino for 3000m / 5000m (he was able to run in front 6 laps in 60", running 6' for 2400m at perfect pace), and somebody else as first pacer.
I remember a top Kenyan (Malakwen) able running 1'44" in 800m, that decided to be professional rabbit for 1500m : I saw this guy running ALONE several times in 2'47" the first 1200m.
Of course, if El Guerrouj tried to beat the WR (and this happened many times, for several years, and before was the same with Morceli), ALL THE OTHER ATHLETES COULD HAVE A FAST PACE, using the same El Guerrouj as referement. This is the technical reason because Ngeny and Lagat were able to run under 3'30" a lot of times.
The organisers, at the moment, ask for pacers for times about 2'50" in 1200m, that it means a final time of 3'32" about, knowing that, at the moment, there are not athletes able to attack any record, and this provokes races slower than the past. In Monaco, the organiser asked (looking for a time under 3'30" from Choge and Laalou) to put the rabbit (Collins Cheboi) only till 1100m, because he can run at a pace for 2'48" in 1200 very well till 100m before, but we were not sure about his possibility to reach 1200m at the same speed. So, because the pacing was very good, and Choge was fully motivated in trying to run fast, finally the race could produce results as some year ago.
About 5000m, the situation is the same : with Bekele (and, before, Gebre or Komen) trying to beat a WR, there were rabbits going for 7'37" in the first 3000m. Now, the only race like this was the first meeting in Doha, when Simotwo was first rabbit in 7'40".
One of the reasons because now it's difficult to find rabbits of the same level of before, is the lack of money in the last period. A top rabbit in the period '95-'02, for an attempt of WR, could receive more than 10,000 USD. Now, we are about 1,500 USD, so who is good is not available. At the same time, also the official prizes of Diamond League are, today, very much smaller than before. Who was n. 9-11 in the 5000m of Oslo (running under 13') received a prize of 200 USD....
When you speak about results, you must know everything about the World of Athletics. You have the idea that, like 50 years ago, the athletes can run for the glory only, but is not true. This is a professional activity ONLY if there is the possibility to produce some good income, for a reasonable period of time. When you have to train a full season, you are able running 3'35" when are very young, and you finish the season with 3,000 USD, the next year you quit any motivation, and you lose your focus. This is the athletics of today, and I'm sorry for this, but, in a period of general crisis, there is nothing to do.
How I already wrote in another message, tha activity for the athletes cannot be divided by the normal situations of their life. It's not a case of EPO, it's a case of opportunities, that today are very much less than before.