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)