On some of your points:-
Coe definitely has to be up there. He carved a huge amount off the previous records and has still today only been surpassed by the two greatest runners over the distance. 1:41.73 in 1981 was - and still is - incredible.
Ovett was a great competitor over the distance but not as great a runner as he was a racer.
Mal Whitfield dominated in a far less international era. Times also do matter. His best of 1:48 as against Snell's 1:44 less than a decade later just doesn't compare. A massive reduction. Snell had a shorter career because he had accomplished everything he had set for himself and he owned md running while he competed.
You have a point about Juantorena. We are biased in his favour because he set a wr in the Olympic final, he also won the 400 at the same Games, and he was a completely different type of 800 runner. He had an aura. But just as an 800 exponent I wouldn't necessarily put him ahead of Wottle and Doubell, who both won Olympic golds and held/equalled the wr at the time.