Did some brief testing of damage dealt rings, specifically the broken promises ring and the fierce ring.
I concluded from my tests that only the ring with the highest roll impacts my damage dealt and that multiple rings increasing damage do not stack.
I had hoped to find this information via searching the discord/reddit/your website for key words but my searches did not give me an answer.
The question I wanted an answer to was if this no damage stacking was the intended behavior by the game devs?
I think the answer will be yes. I suspect in their mind they will see it as them making the game vastly easier than they had originally balanced the game to be.
One of my tests with 19% ring increased my damage from 85 to 94 however that weapon has 34% damage already. I did some math and my number I calculated would be of course be slightly higher but I suspect that I am not accounting for all factors that occur during damage calculation, so I think the 9 damage was an appropriate increase in damage for what the ring said it would do. However under this lens of logic, I do not see why I cannot be permitted to stack 3 of this ring for another tiny damage increase.
I suspect the logic for why these rings do not stack also has to do with giving the player incentive to use different types of rings. The problem I see with that logic is that it is not consistent with how other rings function, this lack of consistency makes me again wonder if the rings not stacking was an oversight or intended behavior.