DP isn't based purely on stats, it is based on in combat performance which is an interaction of a lot of factors, both things like flux but also things like speed and ship system, as well as non-stat card things like weapon selection and placement. Now if a non-Safety Override Brawler was winning 1 on 1 fights with a non-Safety Override Tempest 50% of the time, that might be an argument for a Brawler being worth 8 DP, but last I checked, it doesn't.
Without sim or actual battle success rates, you are not going to be able to determine the DP value properly. The Brawler is the Eagle of frigates. The Eagle is literally a giant pile of stats these days, but its DP value dropped in 0.96 to 20. I'd be curious would your DP assessment on the value of an Eagle versus, say, an Aurora (only 100 less dissipation) or Gryphon (much better flux stats) be?