I've been ruminating on test difficulties etc whilst looking at attempting to have stats of over 100.
One thing that struck me is the names of the difficulty levels:
Easy, Routine, Ordinary, Challenging, Difficult, Hard, Very Hard
These seem fairly objective. If a test is Very Hard, then it's Very Hard. If it wasn't it would be Hard instead, or Difficult. Yet the game sets the tests so that no two people will have the same chance of succeeding on a Very Hard test.
For instance, balancing on the edge of a roof might be Very Hard for a human, but Routine for an Eldar. The test itself is subjective to the person making it. If something is Very Hard then the roll should always be the same, because Very Hard never changes. What does change is the level of difficulty an individual has in attempting to do something.
The chance that a blood thirster succeeds on a Very Hard test should be identical to the chance of a Grot succeeding on a Very Hard test, because the difficulty is the same (Very Hard is Very Hard). What is different is what they are actually doing. A grot might find hiding from a genestealer Very Hard, whilst a Bloodthirster might find trying to pick up a puppy Very Hard. The test is different but the difficulty is the same.
So from this perspective does it make sense for a test to be called 'Very Hard' if the creature making it has a greater than 50% chance of succeeding (ie a statistic of 80 ot more)? Wouldn't a test with 50% chance of success be more like a Challenging test?
I've been thinking for NON opposed tests, where you're just making a roll against a statistic, that the Difficulty should be set to one of seven levels.
This would be for things like Skills etc. You build up your ability to do them:
Very Hard 10%
Only when something is OPPOSED would you actually roll against your statistic, otherwise the chance of success is based on how difficult it is to you.