If I see other mages with buffs outplaying me, I quickly check their buffs, because it's very unlikely that they press their frostbolt button "better" than I do. Each 1% crit is 0,99% extra damage for frost. So if the other mage does 600 dps with ony buff and I do 520 without, I just calculate my 520*1,1 (10% more from missing ony buff) and tadaaa, with ony buff I would have done roughly around 570 dps. If the other mage got flask, he gets around 50 more dps as frost mage (ignoring crit). So I can roughly figure if I did well or if I'm miles away from doing the same ammounts of damage. It's good enough to know that you're good in average. At least for mages damage records depend so much on the perfect raid setup, the perfect bosskill time, crit luck (if u don't crit often enough -> rip dps record) that it's just not worth doing 3 hours or more of preperation each raid, just to eventually be #1 on raidstats.
Also in my life there are more important things like calling my family members or friends, going outside, having fun, eating delicious healthy food, preparing delicous healthy food, rather than comparing to minmaxers, on a private server, in a 11 years old game, who log out every second to save buffs.