So there’s a lot of talk about the Advantage/Disadvantage mechanic that’s been put forward in the D&D N5xt playtests. The basic idea is that when you have favorable circumstances on a roll (most cases I’ve seen people address it as an Attack roll, but it also applies to skill checks and possibly even saving throws) you have Advantage and you roll two d20s and keep the highest. If circumstances are against you (tactically outmaneuvered, or maybe makeshift tools for picking a lock) you have Disadvantage and roll two d20s and keep the lower score.
A little bit ago, Roles, Rules, and Rolls proposed that this really just comes down to a bonus or penalty of about 3.325 or so, on average. He also noted that it’s the effect over the range that matters most, with effectively a +5 at even odds tapering down to minimal benefit (or penalty) for extreme rolls of 1 or 2, 19 or 20. He concluded that it was simple and elegant, and had an “old school” feel.
Just recently I was directed to The Online GM‘s take on the same issue, at about the same time. But unlike RR&R, The Online DM compared Advantage and Disadvantage to other similar mechanics, like the flat -2 for being prone, or +2 for Flanking. He notes that in the mid ranges (where he admits most of D&D lives), (dis)advantage is giving you a swing of +4 or +5, which is huge compared to the older mechanics. At the same time, (dis)advantage has very little effect on the extreme ranges (as noted) — basically, Advantage makes even odds a lot more likely, but generally leaves hard tasks hard; similarly, Disadvantage makes even odds a lot less likely, but generally keeps easy things easy.
Critical Hits follows a very similar line and plots out 2d20 versus a flat +2 bonus, and shows that the +2 bonus out-performs 2d20 at the extremes (and makes a 21 or 22 even possible). Then he plots out +3, +4, and +5 and shows a sort of pyramid pattern, with 2d20 out-performing flat bonuses in the mid ranges and losing effectiveness toward the extremes. That is to say, flat bonuses favor longshots more than Advantage (flat penalties potentially hurt more than Disadvantage) — and in fact, bonuses make otherwise impossible targets (like a DC25) possible and Advantage doesn’t (similarly, Disadvantage makes a DC20 unlikely, but even a -1 penalty makes DC20 impossible).
Finally, the crux of what’s picking at my brain right now, Campaign Mastery takes a look at the patterns beneath all of this, the curved progression of bonuses that 2d20 gives, with plus or minus (almost) 25% when the target is 11 down to plus or minus 5% at the edges. Then he plots that against a graph of target-numbers-based-on-to-hit-bonuses and comes to a number of potent conclusions, the most important of which seems to be this: as your bonus goes up, the effect of either Advantage or Disadvantage goes down. If you’re sufficiently skilled, neither Advantage nor Disadvantage are going to affect your odds much. If you have a high enough AC, you don’t need to worry about being in a tactically Disadvantaged position (because you’ll still be just as hard to hit). If you have a high enough skill, you don’t need to care much about favorable conditions (because the benefit will be marginal). Campaign Mastery concludes that this is an effective foil to min-maxing, and maybe it is, but something about it strikes me wrong.
So what’s the bottom line? I’m not really sure; the math of 2d20 still feels really wonky to me, and adding in flat bonuses as well makes it even more so. I’m trying not to think too hard about how it might interact with the notion of bounded accuracy.
I think it can be summed up as follows:
- Advantage makes easy tasks guaranteed, moderate tasks easy, and difficult tasks are still difficult
- Disadvantage makes difficult tasks very difficult, moderate tasks difficult, and easy tasks are still easy
- (Dis)Advantage doesn’t make impossible tasks possible, or hard tasks impossible, the way flat bonuses and penalties do
- (Dis)Advantage matters progressively less the better you get, meaning that as you improve in skill your tactics and circumstances mean less — so paradoxically, a good Fighter benefits less from good tactics.
In the end, I’m not sure how I feel about the mechanic. It may be I just prefer the devil I know, and I don’t trust this new mechanic which seems difficult to understand by comparison. I know that a +2 bonus gives be a flat +10% likelihood. I really have no idea on a case-by-case basis what Advantage gets me, or how much Disadvantage hurts. And like I’ve mentioned elsewhere, uncertainty and inconsistency are not things I find endearing in a system.