There are three types of skill checks:
- Roll 5d20, take the highest
- roll 1d20
- roll 5d20, take the lowest
Roll 5d20, take the highest:
Insight, and Any knowledge check. Everyone rolls: someone is always going to roll high. Anyone who rolls low will retcon their failed skill check into a successful “aid another” check.
This is why knowledge and Insight checks always succeed. Once one player declares one, everyone else rolls for it too.
A character uses Athletics.
Sometimes you jump over the pit, sometimes you fall in the pit. Just as it should be.
Roll 5d20, take the lowest:
The party tries to use Stealth.
Someone is always going to roll low. This is why no matter how clever their plan is, D&D groups can never avoid combat (that and their “clever plan” is actually really bad). 4e is better in this regard than 3e, where everyone had an opportunity to blow their Hide roll AND their Move Silently roll, but it is still bad.
Given the numerical variance between “roll 5d20, drop the 4 lowest” and “roll 5d20, drop the 4 highest”, it’s really hard to set universal, memorable DCs that can be used for all skills.
In the past, I’ve dealt with this problem by using a variation of the mechanism suggested in the 4e DMG: asking the party to do a single skill check, using their most knowledgeable PC for knowledge checks and their least stealthy character for stealth checks. It’s an improvement, but it’s sad that the guy with the second-highest Knowledge check is basically useless and has wasted his skill investment.
The DMG2 has some great advice about doing group checks, specifically Stealth checks. Everyone rolls their Stealth, and if at least half of party succeed, the group check is successful.
This is a totally great rule. It’s a perfect fix for Stealth. It’s a shame that it’s tucked in a sidebar in the DMG2, not in the DMG1, or the PHB skill section, so that more DMs won’t read it; the “one bad roll screws up the whole plan” syndrome is implied by the Stealth rules and, in my experience as a player, is almost universally used by DMs. This leads to “screw it, let’s do a frontal assault” syndrome, which eliminates a lot of possibilities for sneaky fun, or “let’s send the thief in alone” syndrome, which often leads to thief death.
I wonder whether the same rule shouldn’t be used for knowledge checks. Instead of everyone individually making a check, everyone pieces together their knowledge. If half or more of the party succeeds, the party remembers that beholders are evil, or whatever. This would mean that you don’t have to set knowledge DCs insanely high to challenge the wizard: you can use moderate DCs. The wizard is still helpful, pitching an automatic success, and the second-smartest guy still gets to contribute.