This has likely been hashed out before. Courtesy of this tool:
I've been playing around with that the Gathering Storm 4 black total darkness means vs the 1 Challenge die "blinded condition".
In my game I have always realized that 4 black is tougher in terms of success and been clear that "blinded" means more "sight impaired as by a sudden flash".
However, one thing I dislike about leaving it at that is that the 4 black total darkness does not increase chaos star odds and bumbling about in total darkness should absolutely increase chaos star odds!
So I think the solution is that total darkness is 2 black and 1 Challenge die added.
Taking sample character (I've used more than one and think it works out but here only one given)
An Attack with 5 stat, say Reckless, Trained vs 1 Challenge & 1 Def armour
This usually produces 16% miss, 43% triple success, 13% star
With 2 Black poor light: 27% miss, 31% triple success, 13 % star
With 3 Black very poor light: 35% miss, 25% triple success, 13 % star
With 4 Black "total darkness": 42% miss, 21% triple success, 13 % star
With 1 Challenge blinded: 30% miss, 30% triple success, 23 % star (meaning about the same as poor light 2 black in success just more stars)
Now if 2 Black, 1 Challenge: 43% miss, 20% triple success, 23 % star. That makes the success rates about the same as 4 black but increases the chaos star frequency. It keeps a worsening progression from 3 black for very poor light.
So I propose to keep the 1/2/3 black for worsening light but at no light make it 2 black and a challenge die.
Note, total darkness makes targeting a ranged attack questionable period.
I would keep 4 black for attacking someone/something invisible where you have "general idea of where they are".