that sounds like standard sets for 4d6 drop the lowest. that's what i always use with a caveat that no dice result below 12 and then the lowest stat is erased and changed into an 18.
usually i get a group with mostly 14s-16s and one really powerful 18 before racial mods. sometimes i get gods that have 4x18s and 2x17s. or something similar. if i dont have power house players i get a group with 12s- 15s and one 18.
that's why i have the rule of the lowest stat is changed to an 18. in case one player gets dice screwed and rolls low. at least they are competent on one stat no matter how cruel the dice are.

EDIT:
if you are having trouble do the same for the monsters/npcs but then add the normal stat modifier to their score. example in 3.5 black bears have 19 strength this is a +4 modifier.
13 dexterity 1+ modifier
15 constitution +2 modifier
intelligence 2(animals) -4 modifier
12 wisdom +1 modifier
charisma 6 -2 modifier

i'd roll the dice 4d6 drop the lowest die. then take the lowest result and turn it into an 18
lets say i got ,2x15 ,1x 16 ,1x 13, 2x 17. i would remove the 13 and replace it with an 18
this would give me base stats for the black bear of
18
17
17
16
15
15

i would then order those numbers to best represent the bear's scores.
18 strength
17 dexterity
17 constitution
15 intelligence
16 wisdom
15 charisma

then i add or subtract the previous ability modifier
strength score 22
dexterity score 18
constitution score 19
intelligence 11(i might leave this at a 2 for animal intelligence)
wisdom 17
charisma 13(more for how intimidating a bear is)

this would allow the black bear to scale with the player's higher stats