Let The Dice Decide!

I would like to think I have a creative subconscious, Other people may just be of the opinion that I have really weird dreams.
Multiple Dice
Last night I was dreaming. The dream's protagonist (myself? hard to say in my dreams) was playing some large-scale wargame with models (perhaps toy soldiers too, cannot recall).
Unlike the games of my childhood, this game used dice to determine key events (I wish I had known about such an that idea when I was a kid!).
There were no (apparent) stat-sheets or profiles in my dream, so determining success just needed an established target score, depending on difficulty. Perhaps some of the system was like the Budget Battle game I created years back.
Tank breaking down a gate: a relatively average to easy task. The same tank crossing dragon's teeth and Czech hedgehogs, harder.
I woke up, and the event determination roll reminded me of something I had encountered a few months back.
GURPS uses a 3d6 against a character's relevant skill level or attribute. Difficulty modifiers from -10 to +10 are applied to the skill level (Basic Rules, Book 2 4e p.345), plus lots of other modifiers to offset these.
Rummaging through old emails and saved PDFs, the system I was thinking about was probably PDQ.
In PDQ, a task has a target score of between 5 and 13 on a 2d6, depending on whether it is judged trivial (5) or extremely difficult (13). As may be suspected from the target score of 13 on a 2d6, a character's “quality” in different skills, attributes and fields of knowledge will vary, giving modifiers to the dice roll of between -2 and +6.


My previous reading of PDQ did encourage me to jot down an idea for a simple five-point scale, based on the 3d6 progression 15-13-11-8-6. A roll of 15 or less was needed for a task of trivial difficulty, and a 6 or less needed for something very difficult/unlikely.

2D6, Eleven Descending

Alternately, the possibility of a 2d6 system suggested itself:
Progress would be 11 Trivial, 9 Straightforward, 7 Hard, 5 Difficult, 3 Very Difficult. Odds are obviously going to vary from using a 3d6.
The 2d6 system has the advantage that all you need to do is remember that it starts at 11 and drops in increments of 2. 12 is always a fail.
Rolling a 3 or under is under 10% (8.33%). 5 or less is just over 25% (27.77%). 7 or less is a little under 60% (58.33%). 9 or less over 80% (83.33%) and an 11 or less is 97.22%, so a trivial task is easy, but not totally certain.
If you prefer rolling high for success, simply reverse the progression above and make 2 an automatic failure.
Is this a useful “quick and dirty” way to decide random events? Is the 3d6 or 2d6 preferable? Does the spread need tweaking? Are hard and average tasks too likely to be passed, or need to be less likely? Is the trivial too easy?

Second Attempt, Ten Descending

Thinking further, perhaps a progression starting at 10 might be better. Steps of two, with the end tweaked.
• 10 or less: Easy/Trivial 91.66%
• 8 or less: Average/Medium 72.22%
• 6 or less: Hard/Difficult 41.66%
• 4 or less: Harder/More Difficult 16.66%
• 3 or less: Very Hard/Very Difficult 8.33%