As I said in my last post, I am less than impressed with the skill check system in D&D 4th edition. Most of these problems are rooted in the idea of resolving checks using d20 roll + skill modifier. The high variability and flat probability curve are a nightmare to work with. Actually fixing the problems would require starting from zero, and pitching the d20 heritage, though.
Instead, I just want to hack the skill system a bit, to get it working well enough to be fun. There will likely be several stages to this, but the first starts at the foundation. The baseline DCs in the Dungeon Master’s Guide and in the first batches of errata released for it just do not match the game’s mathematical structure. They need to be replaced.
To develop my numbers, I’ve used three “test cases” – skill modifiers worked up from more or less typical character build cases. Working from these skill mods, I then worked with the success rates I wanted for easy, moderate and hard tasks, to see what DCs I would have to use. Fortunately, there was a lot of “close enough” results between test cases and the number of DCs you need to cover all the bases is reasonable. While I have expanded the number of benchmark DCs for each level from three to four, I’d feared that five or more would be necessary before I started doing the math.
Please note that these DCs are intended only for use in one-off skill checks. Skill Challenges are their own beast, and need to be built from different math.
The test cases I used to derive DCs are:
- Untrained – A character that has 12 (+1) in the relevant stat and no skill training. The character does not acquire magic items relevant to the skill, and does not raise the relevant stat, except at level 11 and level 21 when all stat values increase by 1.
- Trained – The trained character begins with a 16 (+3) in the relevant stat, and is trained in the use of the skill (+5). The character acquires a magic item that helps with skill checks once every fifth level (beginning at level five), the item’s bonus equal to the character’s level divided by five. The character raises the relevant stat at every opportunity.
- “Min-Max” – The trained character begins with a 20 (+5) in the relevant stat (thanks to a racial modifier) and is trained in the use of the skill (+5) and has taken a Skill Focus feat (+3) for this skill. The character acquires a magic item that helps with skill checks once every fifth level (beginning at level five), the item’s bonus equal to the character’s level divided by five. The character raises the relevant stat at every opportunity. Note that, in spite of the label, this is not a true min-max build. There is still room for characters to develop skill mods higher than this, including acquiring a relevant magic item before level 5* the item’s skill bonus.
This resulted in the following Skill modifiers, with a little inaccuracy here and there due to grouping levels into pairs:
Next, I decided what what I felt the approximate success percentages should be for easy, moderate and hard tasks. I settled on 85% for easy, 65% for moderate, and 45% for hard. I’m sure that many readers will find these unusually high – I believe WotC aimed for 50% success for moderate difficulties – but these are supposed to be heroes, so I want to decrease the whiff factor. One reason why I am being so transparent about my methods is to make it easy to adjust my results to suit your own tastes.
My assumptions turned out the following DCs for each typical character for easy, moderate and hard tasks.
|Easy (85%)||Medium (65%)||Hard (45%)||Easy (85%)||Medium (65%)||Hard (45%)||Easy (85%)||Medium (65%)||Hard (45%)|
I decided that easy tasks for the untrained should be “say yes” situations – leave the dice on the table. I also conflated similar columns, like hard for untrained characters and easy for trained characters. That led to the following set of benchmark DCs:
To settle on an appropriate DC for a Skill check, determine which test case is closest to the best character in the party at that skill. Then assign the DC for a character of that level based on your estimate of the task’s difficulty as follows:
So far, I’ve only used these DCs in one session with Level 1 characters, so they are not battle-tested. Nevertheless, I already like them much better than what WotC has given us.
Use them in good health.