Saturday, August 6, 2011

Skill Math: A look behind the new Skill DC tables

Skills. It’s not an issue I cover much on this blog, mostly because I like to focus on combat-related rules topics, and because I tend to consider the skill system a poorly implemented mess: not broken beyond hope, but in need of a good overhaul. That said, It’s fair to point out that the skill framework did receive a significant improvement last year with the release of the new skill DC tables with revised math that actually matches skill bonus progression. Unfortunately, this update somehow didn’t make it to the errata compilations, and players who didn’t buy the Essentials books haven’t had the chance to use it.

Rather than reproducing the whole tables (which have entries for each level, and three degrees of difficulty), I have worked out some relatively simple formulas that give a good approximation of the DCs per level. Though not trivial, they are relatively easy to memorize so as not to need to consult any reference book while you play - I know I’m tired of looking for my copies of Heroes of the Fallen Lands or Forgotten Kingdoms in the middle of a game.

They are the following:

Easy DC:                7 + 0.55*Level
Moderate DC:   11 + 0.7*Level
Hard DC:              18 + 0.8*Level

Unlike most calculations in 4E, you should round these values to the nearest integer - so, as an example, the level 1 DCs will be 8, 12, and 19, respectively. These DCs have been chosen so that an incompetent PC using an untrained skill based on a tertiary ability will succeed on Easy checks roughly 60% of the time, whereas an expert PC with training on a skill and a primary ability score on it should pass 60% of Hard DC checks. Moderate DC is adjusted for PCs with either skill training or primary abilities on a skill, and they should succeed 60% of the time. The drawback of this approach is that the difference between Easy, Moderate and Hard is not constant across levels, and gets to be quite high at level 30 - DCs of 25, 33, and 42, respectively - meaning that, eventually, a character capable of succeeding on a Hard DC will never fail an easy DC, and vice versa.

It’s still possible to break these DC values by stacking skill bonuses, which can get pretty ridiculous when combining feats, backgrounds, and magic items. However, as long as you don’t put much effort into breaking it, the system will work fine. This is not the solution I would have chosen for skill progression (I may talk about that at some point in the future), but it is the only one that makes skills playable without having to adjust dozens of game elements.

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