One is additive and the other is multiplicative.
I understand the concept of additive and multiplicative but your elaboration is pretty vague, e.g. 2+2 = 2x2. You need to accompany your elaboration with examples.
Percentage (%) is always a product(multiply) of something, e.g. Base + (5% of Base) = Base x 105%. The only time percentage is addition is that it has the same product, e.g. Base x (5% of Base + 5% of Base).
Anyway, I have not done extensive testing. So it all boils down to the damage formula.
It can be Base + Finesse Bonus + Ranged Bonus + Elevation Bonus.
It can also be [Base + Finesse Bonus + Ranged Bonus] + Elevation Bonus.
It can also be [[[Base + Finesse Bonus] + Ranged Bonus] + Elevation Bonus]
So Huntsman maybe justifiable after all. But the downside is that some fight doesn't have elevation at all. Peace.