the thing to recall with mass low hd characters, is to use group tactics. specifically, the aid another action. if one person is trying to hit, and you need a 19 or 20 to hit, if the 3 or 4 adjacent allies of the enemies use the aid another action and succeed, that is +2 to hit per success. makes that 19-20 drop to 11-20.
especially if the enemies have reach weapons. if you use the move actions to swarm around a given pc, you can have up to 5 enemies within 5', assuming one to the right, one to the left, and three in front (two on the diagonals). that makes 9 additional enemies within 10' who only need a 5' reach weapon to hit. if they have a 10' reach weapons, you can have a third layer too.
given five individuals all attacking one pc, the four can give the remaining one a +8 to hit... useful for tripping, sundering, bullrushing, grappling, and plain old attacking.
so given your large group against the party, the party could have been slaughtered.
for the players side: cleave, AoE, and skill checks become necessary to attempt to take on such an encounter. group intimidate is a good option.