Can I use the Monster Stats in the DMG to estimate a party's damage output?

Question

I'm designing an encounter where the party has to hold off hordes of baddies that are trying to break through a set of doors, so designing the encounter really hinges on how much damage per round the party can dish out. Basically I'm creating what would be a minion battle in 4e.

On page 274 of the DMG, under Monster Statistics by Challenge Rating, each CR level of monster is given an approximate damage amount it can do per round, which is intended to be "a fair challenge for a party of four players".

For purposes of estimating how much damage a party of a given level might deal out per round, is it safe to use these numbers as an estimate, or am I running a sausage factory backwards and hoping to make pigs? If not, is there a more accurate resource for damage-per-round estimation, or a better way to design such an encounter altogether?

(note: this is for eventual publication, so I don't have a specific party to calculate numbers for. I'm interested in an average party's damage output per round, if such a thing can be estimated)

Answer 1

No

At least, not like that.

On page 274 of the DMG, under Monster Statistics by Challenge Rating, each CR level of monster is given an approximate damage amount it can do per round, which is intended to be "a fair challenge for a party of four players".

A "fair challenge" is one where the party has to expend some resources and feel challenged, but is ultimately expected to win. It does not mean a toss-up with equal chances of winning or losing. In a "fair challenge", the PCs are at a marked advantage, so any average stats for the adversaries are not a good reference for the same PC stats.

A better method would be to evaluate monster AC and HP together with expected combat length to estimate PC damage-per-round.

Ultimately, the best solution is to playtest.

Answer 2

Average damage per round is not useful for encounter building

The problem with using an average damage output to build an encounter is that damage is highly variable with party composition and with player decisions. For example, a party of 4 level 5 wizards could choose to cast Fireball in the first two rounds, for 4 * 8d6 * (# of enemies hit) damage in the first two rounds, and then be reduced to cantrips for the rest of the battle. On the other hand, if you have a party of 4 rogues, they can pull off sneak attacks round after round forever. Thus, the average damage per round of the wizards drops significantly the longer the battle goes, whereas the damage per round of the rogues stays roughly constant.

Since the PCs are fighting a horde, I've also observed that players will conserve their most powerful abilities for the eventual boss (whether or not there really is a boss at the end). Therefore, they will likely be fighting at lower than maximum DPR against the horde.

Use normal encounter building rules

While the 5e DMG encounter building rules do skew a bit toward the easy side, I think you should use the standard encounter building rules to build your horde fight (DMG 83):

Sometimes an encounter features multiple enemies that the party doesn't face all at once. For example, monsters might come at the party in waves. For such encounters, treat each discrete part or wave as a separate encounter for the purpose of determining its difficulty.

A party can't benefit from a short rest between parts of a multipart encounter, so they won't be able to spend Hit Dice to regain hit points or recover any abilities that require a short rest to regain. As a rule, if the adjusted XP value for the monsters in a multipart encounter is higher than one-third of the party's expected XP total for the adventuring day (see "The Adventuring Day," below), the encounter is going to be tougher than the sum of its parts.

Answer 3

No, probably not.

I'm pretty sure there's nothing in the official sources that would indicate that you can use the referenced table to estimate player damage.

In fact, I don't think such a table would make any sense, since different classes will deal different amounts of damage.
For example, bards have barely any spells that primarily deal damage, and instead focus on support spells that buff and heal their allies or debuff their enemies.
Wizards, on the other hand, can do pretty much anything aside from healing (Life Transference aside), and are especially good at dealing massive damage.

Of course, the same thing is the case for monsters. However, you will (hopefully) fight more than one encounter during a campaign, so you can use an overall average. Your party, on the other hand, will stay the same for the entire campaign (unless someone dies or a new guy/gal joins).

Answer 4

Not generally.

For a specific party, you could simulate the encounter by knowing the spells they have selected, the strategies they will use, and how much AoE damage they have available to them. However, as others have pointed out, this is not a great solution because:

A) it's a lot of work

B) it only works for that party

C) it is highly dependent on party makeup (for examples, a party of wizards with lots of AoE spells can take out more minion level monsters quickly than a party of fighters)

D) damage is random, and a bad roll could really screw things up.

If you are going to be fighting many minions, you may want to consider using the mass combat rules from UA, or at least stealing some of their ideas (if you do, be sure to look at the older revision as well) and incorporating them into your own game.