In Game DPS Meter

[Tashigi]

If every boss fight was tank n spank you would have an argument.

You're hellbent on opposing the notion of any form of a DPS parser, we get it.
He has an argument. Once DPS is calculated, you can simply substract based on how long you stay away from the target, due to dodging red zones, or whatever other silly mechanics the boss may throw at you.
This is commonly calculated by the average DPS meters found in other games and the existing ones for this game, as well.

And before you you jump in and start nonsense about how dodging is more important than your damage dealt: Enrage mechanics.
Sometimes it's better to eat damage to max your entire group's output.
Again, another common sense tactic.