I'm designing some adventures and one of the issues I'm thinking about is how to come up with a reasonable range of difficulty ratings to challenge adventurers.
Knowing the party is key, but if i'm designing something where I don't know the characters, then I'd need some baseline to work from. After thinking a bit about this, I figured in most groups there would be someone qualified (many ranks in a skill) to make a decent attempt at most tasks. However, the question is what is considered decent? 50% , 60% or 80% chance of success? Yeah, it probably depends on what the challenge is, but coming up with a reasonable range of possibilities would help.
I worked out a chart which shows a moderate advancement over levels of one skill for a character - probably his key skill. I assumed the character wouldn't spend more than 50% of his CPs per level on the skill, but still spend a decent amount to progress; also assume a stat of 20. Then i worked out the TNs he would have a 100%, 55% and 1% chance of success against. This then gives me a decent range of base DRs. Of course this doesn't factor in stat bonuses, imploding/exploding rolls, fate points and so on, but gives me an overall starting point.
How do you all come up with DRs? Is this this type of chart useful?