I do not post much, but I have been playing this game on and off for nearly 10 years and have a pretty good grasp on the game. That being said, here is what I believe has been done:
As far as I can tell from my own testing and gathering data from other economic dpp focused hunters, what they have pretty much done is taken away a lot of the penalties that used to be there for playing inefficiently. They accomplished this by lowering the base loot multipliers on most mobs, while raising the compensation for decay and adding/buffing the compensation for healing and armor decay.
In theory, this would make loot slightly to moderately better for people who were using unmaxed guns, guns without high dpp, or using armor/healing more than absolutely necessary. On the other hand, those of us who focused on dpp and being as efficient as possible will see worse returns. The ability to profit on TT returns using high dpp setups, especially hunting smaller hp mobs, has been significantly nerfed as a result of this, which is likely paying for the increased loot for the rest of the player base.
Now I admit that it is still really early, and I am not claiming 100% certainty on any of this, but everything I have seen in my own game play, the game play of those I know personally in game, and what I have read on this forum all point to me being pretty close here. Personally, I am likely to be scaling back my hunting as what I enjoyed about the profession has been nerfed into the ground.
To get back to the OP question, if I am even remotely correct you are better off using that non SIB unmaxed weapon now than any other time in recent memory.