It's funny how you just missed my point there.
shao32 already said it, O8s just represents a small number of people who have actually cleared Sigma.
3 months ago, only ~3% of EU/NA have actually cleared Sigma.
So, 3% of the best players only are represented in those graphs. You can't call that "low skill".
To actually show the difference of well played and bad played tanks, we
need a more common duty. And O6s provides more uptime than O8s, too.
Also, we are
not comparing tank DPS difference to rDPS. That doesn't make any sense.