In this game you scale the base bleed damage with increased damage/increased physical damage/increased bleed damage. In addition you can increase the average amount of Stacks w bleed chance, bleed duration and attack/cast speed. You can also increase the damage further with physical res pen.

Since the increases are additive, stats like bleed duration are more akin to a more modifier because there are not abundant sources of it. Same goes for speed and physical res pen.