It will work. It's basically Action, and before that, Fuzion. I would use:
Atts range 1 to 5
Skills range 1 to 5
Roll 3d6
Success if sum >= target number
Degrees of success = (sum - TN)/2.
A TN if 12 night be too easy, depending on how many points players start with.
TN12 was taken from Action. It was used for actions which are of easy/average difficulty (i.e. are of dramatic relevance to the adventure, not just rolling for the sake of it). Action represents increased difficulty by raising TN, but I decided to take a page from PbtA and keep TN fixed. Increased difficulty is represented by applying penalties to the roll result, which keeps the probabilities the same. The difference between the roll result and the TN determines the degree of success.
For example, the tech wiz Jim is trying to hotwire a crashed alien spacecraft. He's a genius with lots of training, so his Att+Skill bonus is +10. This makes all but the most difficult tasks easy for him. Since he's dealing with an insanely complex alien spacecraft, he takes a -10 penalty due to unfamiliarity with the specs, the complexity of the task, compensating for the damage to the craft, a lack of proper tools, etc.
The final result of the roll determines the degree of success. Since his modifier has been reduced to +0, he is slightly more likely to fail than to succeed since the average result is 10-11 and he needs to score at least a 12.
You're concerned that it might be too easy. Why is that a problem in the first place?
We can adjust the degrees of success to produce interesting results, such as success at a cost or interesting failure.
If Jim fails to hotwire the ship, then he falls prey to whatever problem forced him to try. If he succeeds at a cost, then the ship flies but piloting will be hell. If he succeeds, then he escapes his predicament. If he succeeds critically, then he quickly arrives at a hospital planet where the nurses are sexbots. If he critically fails, then the hotwire goes great until the ship suddenly appears in the middle of an unrelated active warzone.
That's a pretty significant tweak. The way you phrase it, it sounds like if you can't know difficulty class/level, you won't know what your odds of success are, and given this was your original complaint about dice pools -- that the varying sliders made it too difficult to calculate odds -- I just wasn't seeing how this solved that problem.
I don't understand what you mean here. Do you normally tell your players their exact odds of success?
I had several complaints which applied in different circumstances. The way I devised this is that I want the GM to tell the player of any modifiers than the character should reasonably know about, while being free to conceal modifiers that they should not. This addresses
a big flaw in the Chronicles of Darkness task resolution mechanic: the GM cannot conceal any modifiers from the players since all modifiers are applied before rolling. Trying to fix it by subtracting successes after the fact is clunky.
The task resolution mechanic I proposed fixes this by the inherent nature of XdY+Z resolution mechanics: there is only ever a single probability slider. Modifying the roll result or the target number are equivalent and easy to do. Concealing modifiers from players is easy to do, as they only learn after the roll is made by observing the results.
That, I suspect, is down to a psychological effect that derives from the players, not the mechanics: a lot of players like the chance to make an active defense roll, even if in practice the odds of a beneficial result are the same, because it reinforces the illusion of "doing something" in a combat rather than sitting and waiting to passively find out what happens.
It's really frustrating, tho, because I generally prefer mechanics that reduce the number of rolls rather than increasing them. Tabletop isn't like video games where the computer rolls the dice for you. If you're not an expert, then any situation where lots of dice must be rolled might take hours.
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That reminds me. I'd really like a critical fail mechanic that lets the GM conceal a critical fail from the players until he can spring the consequences in a dramatic moment. As opposed to GM fiat, which feels mean spirited.
Maybe a luck stat for PCs that only the GM can roll? I'm not a fan of dissociative mechanics so I prefer to keep luck in the GM's hands and hero points (or whatever the name is, but it represents a PC's sheer stubborness, willpower, etc) for players.