You're misunderstanding the data in-front of you.
The variation between the top and bottom percentiles is governed by the enrage timer, the tighter the enrage, the tighter the variation. O4S drops that difference to under 10% because that's all the slack the encounter gives you. Any more and
A) You wipe to enrage thus
B) The run doesn't get shown in the statistics you're looking at.
A better approach would be to look at a 'rough' (
And believe me, it pains me to refer to it this way) encounter where enrage isn't a problem.
First up, Hashmal, he is a good halfway house between early savage content and a punching bag, he does kill people, he does have a couple of DPS checks and it's possible for a raid to hit a point where things are unrecoverable. However, there isn't an enrage timer that I've ever seen, thus the carry potential and skill variance is massively increased.
Jobs at 10% -
Jobs at 90% -
Jobs at 99%
In the above data, there's between a 200% and 300% disparity from 10 to 90 percentile. Go to 99 percentile and you're adding another 50% ontop of that again.
TLDR: The DPS difference between 'good' and 'bad' teams and players is so much bigger than 20%. Some evidence to support this is linked above if you are in anyway interested in reading it (I suspect you are not).
Not really interested in the rest of your arguments as it's about as grounded in reality as a Brexit campaign.