just give everyone armor of hvy fortification and dont even worry about it

. But seriously, I you take a monster that requires say a sixteen to hit and then applied basic math to it.
(lets say that they flank together)
1st level ftr (human): (str 16, dex,con,wis,int,cha 13)
feats (wep foc, dodge, mobility )
bab +5 Damage 2d6 +4 crit 19d-20x2
rogue (halfling): (dex 16, others 13)
feats (wep foc)
bab +6/+6/+6 damage 1 x2 + 1d6 sneak attack
Against AC 16
so the ftr who has 50% chance to hit and a 5% to crit hit, has a mean damage of 6.6 per round
the rogue has a 55% chance to hit and a 2.5% to crit with three attacks does 7.8375 damage in one round
level 4 ftr
feats (dodge, wep foc, mobility, Spring attack, wep spec)
bab +8 damage 2d6 + 6 19-20x2
level 4 rog
feats (wep foc, dodge)
bab +8/+8/+8 damage 1 x2 +2d6
against AC 19
Both have 50% chance to hit.
ftr has 5% chance to crit and does mean 7.8 damage a round
rogue has 2.5% chance to crit and does mean 12.225 damage a round
20th level ftr
feats (wep foc, wep spec, dodge, mobility, Sprg atk, expertise, whirlwind atk, power atk, cleave, great cleave, sunder, improved sunder, improved trip, mounted combat, trample, ride-by attack, spirited charge, point blank shot, improved crit)
bab +24/+19/+14/+9
damage 2d6 +6 17-20x2
20th level rogue
feats (wep foc, dodge, mobility, expertise, improved crit, point blank shot, rapid shot)
bab +18/+18/+18/+18/+18/+18/+13/+13/+13/+8/+8/+8/
damage 1 19-20x2 +10d6
against AC 35
big math here so just trust me on this one.
ftr has mean damage of 17.55 a round
rog has mean damage of 60.9 a round
I'm almost sure these figures are off as I did it in about 5 min, but they are kinda close.