D&D 5E What's up with Vicious Mockery?

[Tony Vargas]

I love this thread. The funny part is as a re-entry DM (back to doing it after a long hiatus from RPGs) I got caught off guard with my rather large party of 7 players (all level 2) including 2 Bards.

I can't say I recall ever having seen two bards in the same party prior to 5e.

 

[Ovinomancer]

A successful Vicious Mockery effectively gives roughly a +5 AC to the next person attacked by that target,

It does not do this. I do wish I could completely stomp this out. It's not just technically wrong, it's also just misleading.

 

[Mistwell]

It does not do this. I do wish I could completely stomp this out. It's not just technically wrong, it's also just misleading.

Are you arguing disadvantage is not the rough equivalent to -5, or that -5 to the attack is not the rough equivalent to +5 to the AC they're attacking?

 

[Ovinomancer]

Are you arguing disadvantage is not the rough equivalent to -5, or that -5 to the attack is not the rough equivalent to +5 to the AC they're attacking?

Former.

 

[Mistwell]

Former.

Why is disadvantage not the rough equivalent to -5? The PHB lists the value as 5 for passive checks from advantage/disadvantage.

From here, where they crunch the math, "The general rule of thumb that in the mid range of the d20 (from success on a 9+ to 12+) advantage grant roughly a equivalent to a +5 bonus and disadvantage a -5 penalty. "

and

"The PHB provides a short cut for applying advantage via a +5 modifier to supplant the roll. Coincidently

6.650 - (6.650-3.325)/2 = 4.9875 ~ 5"

 

[Ovinomancer]

Why is disadvantage not the rough equivalent to -5? The PHB lists the value as 5 for passive checks from advantage/disadvantage.

From here, where they crunch the math, "The general rule of thumb that in the mid range of the d20 (from success on a 9+ to 12+) advantage grant roughly a equivalent to a +5 bonus and disadvantage a -5 penalty. "

and

"The PHB provides a short cut for applying advantage via a +5 modifier to supplant the roll. Coincidently

6.650 - (6.650-3.325)/2 = 4.9875 ~ 5"

Well, as I said, it's technically incorrect. For starters, you can't map a triangular distribution to a flat bonus without losing lots of information (which you are). Secondly, the impact is not the same. If the disad target needed an 16 to hit you, shield makes you unhittable except on a crit, but disadvantage does not (it reduces your chance of being hit from 4/20 to 16/400, or from 20% to roughly 4%. This is actually a titch better than shield in this regard. If the target can only hit you on a 20, shield does nothing for you, but disadvantage makes the odds of hitting you go from 5% to 0.25%.

On the other side, if the target needs a 7 to hit you, shield changes your chances of being hit from 70% to 45%. Disadvantage changes those chances from 70% to 49%, or almost a full "point" less than shield. This is, of course, misleading again, because shield doesn't protect you from crits, but disad does no matter what the target number needed is by strongly reducing the chance of a critical hit.

On to the mean! The mean of advantage is 13.82 with a standard deviation of 4.71. This means that roughly 67% of all rolls with be between an 18 and a 9. Contrasted with a straight d20 with a mean of 10.5 and an sd of 5.77, making 67% of all rolls between 5 and 16 (which is 13/20 options or 65%, so, duh). The difference at the edges is 4 at the low end and 2 at the high end. This doesn't at all look like a flat +5.

And, while at exactly 10, the chances of rolling at least a 15 on advantage vs a straight +5 matches very closely, it quickly diverges. By the time you get to the chance for rolling a 21, they're infinitely far apart. This does, however, illustrate the +5 to passive rolls mechanic of advantage -- considering that you're assuming a roll of a 10 already, this is a very quick and fairly adequate shortcut, but it holds only on assumed rolls over time (like passive scores are meant to represent). If you actually roll, the differences are quickly apparent.

So, yeah, it's technically wrong on many counts, but it's also misleading because the +5 comparison only holds in specific circumstances in a very narrow range (pretty much 9-12) and if you're far outside this (like say near 18) it's an assumption that will mislead you pretty badly as to what your actual chances are. It needs to die as a meme.

 

[The Crimson Binome]

Why is disadvantage not the rough equivalent to -5? The PHB lists the value as 5 for passive checks from advantage/disadvantage.

From here, where they crunch the math, "The general rule of thumb that in the mid range of the d20 (from success on a 9+ to 12+) advantage grant roughly a equivalent to a +5 bonus and disadvantage a -5 penalty. "

It's the equivalent of -5, if you're operating at the middle of the die range, but who does that? Characters don't often take actions that have an even chance of success or failure. Most gameplay involves specialists doing the thing that they're specialized in, or using abilities that target someone's worst save.

 

[Eubani]

Keep in mind that Bards are magically designed for buffing, debuffing and indirect magical effects instead of damage. If everybody did close to the same amount of damage the Fighter may as well go hang himself as that is all he has. The spellcasting Bard is a tool of subtlety not a beat stick.

 

[Dausuul]

Rough equivalent does not mean exactly equal in 100% of circumstances.

The typical use case for vicious mockery is a PC casting it on a monster. The monster is seldom a versatile combatant choosing from a wide array of options. It usually has few if any options other than "beat somebody over the head." It can also be expected to have a midrange attack bonus giving it somewhere around a 50-65% chance to hit (depending on the monster and the target). Disadvantage will reduce this by somewhere between 22.75 and 25 percentage points.

Thus, "roughly -5" is a perfectly good estimate in this scenario. In fact, it is a fairly good estimate in most scenarios. Crits have a negligible impact on overall damage unless you have a special ability to exploit crits in some way (e.g., a vorpal sword or paladin smite), and standard deviation is irrelevant when there are only two possible outcomes ("hit" or "miss") and the probability of each can be computed exactly.

 

[Ovinomancer]

Rough equivalent does not mean exactly equal in 100% of circumstances.

The typical use case for vicious mockery is a PC casting it on a monster. The monster is seldom a versatile combatant choosing from a wide array of options. It usually has few if any options other than "beat somebody over the head." It can also be expected to have a midrange attack bonus giving it somewhere around a 50-65% chance to hit (depending on the monster and the target). Disadvantage will reduce this by somewhere between 22.75 and 25 percentage points.

Thus, "roughly -5" is a perfectly good estimate in this scenario. In fact, it is a fairly good estimate in most scenarios. Crits have a negligible impact on overall damage unless you have a special ability to exploit crits in some way (e.g., a vorpal sword or paladin smite), and standard deviation is irrelevant when there are only two possible outcomes ("hit" or "miss") and the probability of each can be computed exactly.

I disagree strongly with this assessment of the usual roll needed. The CR system means that parties are often facing solo or duo threats that are significantly more likely to land attacks or threats that have smaller bonuses but are nunerically superior. It also ignores that many parties have a large disparity in ACs, usually larger than the sweet spot is wide. I find this to be a flawed assumption.

And crits are often bad from the monster side when facing solo or duo threats. Sure, that mob of kobolds, not so much. A hill giant walloping you for 4d12 is not negligible. Crits break the assumption of how many more hits/rounds ypu can last, and I've had more than one combat go suddenly wrong for the players due to a crit.