Okay, my issue isn't the usual "synth should or should not break at 100% (0 dura)" arguement. I agree if dura is 0, synth should fail, even at 100%.
My problem is a little different. In a nutshell, I feel like a lot of the "break @ 100%" situations are not justified because the last synth attempt often overcharges your dura. Let me elaborate:
First a quick recap of the outcome of "Standard Synthesis", not counting when unstable:
[Perfect Success] (high pitch sound effect)
Progress usually: 15 ~ 20max
Dura Loss usually: 0 ~ 4
[Adequate Success]
Progress usually: 10 ~ 20max
Dura Loss usually: 5 ~ 9
[Fail]
Progress usually: 0 ~ 10max
Dura Loss usually: 10 ~ 15
Most people would agree those are pretty good estimates of standard synth with a stable core. Now to explain the actual issue. Below is an example of what currently happens in the game.
_ _ _
Prog 97% & Dura 4
>Standard - Adequate Success "Prog increases 20%, Dura decreases 7"
Prog 100% & Dura 0
>BREAK
You work a synth up till 97%/4dura, you do 1 more synth, and break at 100%, but I call BS on that. Why is the game allowing your progress to go over 100%? In reality that's telling me, "you're gonna spend 7 dura to work this synth to 117%" ....wtf?
The game should NOT let you do more work than needed to finish the synth. Here you can make the arguement, "If the game wants to charge you dura for over 100% progress, then it should also let you complete an item with 0 dura. It's unfair to have one without the other."
But honestly, I think it would be better to have neither and tweak the system. What should've happened just now was something like this:
Prog 97% & Dura 4
>Standard - Adequate Success "Prog increases 3%, Dura decreases 1"
Prog 100% & Dura 3
>SUCCESS
See this makes sense to me. This says, "the random number generator in the game said you should've spent 7dura for 20% prog, but since you can only go 3% more, you will only lose a proportional amount, which is 1 dura".
_ _ _
Again, right now:
Prog 94% & Dura 7
>Standard - Fail "Prog increases 10%, Dura decreases 8"
Prog 100% & Dura 0
>BREAK
Spending 8 dura to get to 104% ... makes no sense. It should be:
Prog 94% & Dura 7
>Standard - Fail "Prog increases 6%, Dura decreases 5"
Prog 100% & Dura 2
>SUCCESS
This is a fair outcome. "Random Num Generator said you should've spent 8 dura to work 10%, but since you can't go further than 6%, you only lose 5". Do the math: (8/10)*(x/6) ==>> 10x=48 ==>> x=4.8 ==> 5 dura for 6%
_ _ _
Now I'm not sure if the game rolls the dice to determine if each Standard synth should be a [Perfect Success], [Adequate Success], or [Fail] first, and then uses that in another dice roll to see what your Prog/Dura will be ..... or if it figures out your Prog/Dura first, and that determines your [PS] [AS] [F] outcome. Either way, it should not matter. The game should operate on the simple fact that, "It should cost less durability to make 7% prog than it does to make 20% prog."
Crafting should be tweaked such that your progress from all synthesis attempts should not exceed 100%, and thus, the last synth attempt should have it's calculation adjusted so the possible dura loss will match the possible progress.
That being said, if this WAS implented, it would not eliminate all "break @ 100%" situations, but it would definitely reduce the occurences that happen; plus it would make the ones that do break easier to swallow.