I'm sitting here wondering the same thing. The flat damage has to apply somehow to the ailment right? Does anyone know what the base damage of an ailment is based on?

It's super hard to test on my high level character, I'll probably just have to make a new character and mess with a point at a time or something.

share what you figure our :).

The base is determined solely by your character level, and then increased only by the general ailment damage % you have + the ailment damage % you have for that specific ailment. No flat damage that I could find anywhere was added to ailment damage, nor did weapon damage or the damage of the type that inflicts the ailment make any difference. So for example +Material damage and +Rend damage do not affect Bleed in any way (other than determining what status ailment you inflict on Physical hits, based on which is your highest damage type), neither flat damage nor % damage.

@abaddon if this is correct then I wonder how endgame itemization will feel.

Non-ailment builds can scale with weapon damage {attack only}, +flat dmg to {spells/attacks}, %dmg type, {attack/cast} speed, crit. Ailment builds would only be scaling at full value from %ailment dmg. atk/cast speed and %ailment chance have an upper limit in usefulness and limit each other as well. (Once you are able to reach max stacks quickly there is no more benefit to either stat; though it is difficult to know when that happens)

At least we can add more dimensions to itemization with Primordial Insight (major passive). It might be enough?

I am not complaining, just thinking out loud. I have not experienced high level gameplay yet. Time will tell.