Im not much use when it comes to calculating odds. But I feel that a progressive system or two in place would help to avoid alot of the rng, made, I added a thought on it in this other post today
Short version of it. Do missions, get an option to target a modifier or more that you wanna increase, either using current materials or some new material, The closer you wanna get to 100% modifier the more costly it will get but at least you know you’ll get there in time.
This can be done to all rng in the game, just dont make it too easy but give us a choice to perfect a few items in time