Really... no benefits? Something tells me different on this all-time list.
http://www.alltime-athletics.com/mmaraok.htm
My original point wasn't to say with 100% certainty that Dibaba, Hassan, and Kipyego are all clean but that the women's 1500m historically has not had any East Africans with talent participating.
Imagine the top men's list with Chinese and Russians leading it, even doped that list would suck. Much like the men, the genetics make a big difference, so either A) the new crop of Ethiopians/Kenyans are more talented and not doped B) they are equally talented (I find this hard to believe) and equally doped C) more talented, same doped...same times (not likely either)
You choose, either Dibaba's natural talents are just as good as 10 other Chinese women, both just doped like crazy or she is just something way better than we've seen.