I do use NPC settlement generation rules for monsters, but not Monte's abysmal demographics; I use 1/4 are 2nd level, 1/8 3rd, 1/16 4th and so on up. For gnolls that would mean 1/4 are War-1 (etc) on top of racial hd, 1/8 Wr-2, 1/16 War-3, 1/32 4th, 1/64 5th, 1/128 6th, 1/256 7th (ie War-7 + 2hd, a 9d8 critter). If they have PC classes they're 1 level lower, eg Ranger-6 instead of War-7.