Majere said:
If that is the case, Im a happy bunny, just seems that getting a D8+3D6+1 weapon for the same as a D6+4 weapon seems a little broken.
Time for more scheming in my weapon building programme.
But the +4 weapon has +3 more to hit, the extra damage is multiplied on a crit, and it's not subject to elemental resistance.
A +4-equivalent weapon is something you might have around level 13, so let's compare a 13th level fighter with bastardsword +4 to one with a flaming frost shocking bastardsword +1 against some CR 13 monsters from the MM.
Both fighters have a BAB of +13, an effective Str of 22 (+6), the whole Weapon Focus/Specialization chain, and Improved Critical. Thus, fighter 1 has an attack bonus of +25 with a damage of 1d10+14 (average 23.4 including crits), and fighter 2 has a bonus of +22 with a damage of 1d10+11+3d6 elemental (average 19.8 + elemental). We'll compare them to a glabrezu, an adult green dragon, a storm giant, a mummy lord and a death slaad. I'm assuming there's someone in the party who can give the weapon a proper alignment, but that the weapon is not made out of any special material.
Glabrezu: AC 27. Immune to electricity, and has fire/cold resistance 10. Fighter 1 hits on a 2, 7 and 12 for a total of (0.95+0.7+0.45)*23.4 = 49 damage. Fighter 2 hits on 5, 10 and 15 for a total of (0.8+0.55+0.3)*19.8 = 39 damage. DR is 10/good and thus bypassed.
Adult green dragon: AC 27. Takes full damage from the elements, so the elemental sword does 3d6 more per hit, for a total of 59 points of damage.
Storm giant: AC 27. Immune to electricity. Same base damage as above, but Fighter 2 does 2d6 more per hit on account of elemental damages, for a total of 52 damage.
Mummy Lord: AC 30. Fire resistance 10, so no extra fire damage. DR 5/-. Immune to crits. Fighter 1 does 1d10+9 per blow, average 14.5. Fighter 2 does 1d10+6+2d6, average 18.5. Fighter 1 hits on 5, 10 and 15 for a total of (0.8+0.55+0.3)*14.5 = 24 points. Fighter 2 hits on 8, 13 and 18 for a total of (0.65+0.4+0.15)*18.5 = 22 points.
Death slaad. AC 28. Fire/Cold/Electric resistance 5, so the average bonus damage from the elemental sword will be 0.5 points (1/6 per element). DR 10/Lawful, which is bypassed. Fighter 1 hits on 3, 8 and 13 for (0.9+0.65+0.4)*23.4 = 46 points. Fighter 2 hits on 6, 11 and 16 for a total of (0.75+0.5+0.25)*20.3 = 30 points.
In these five cases, the weapon with enhancement bonus instead of elemental damage did more significantly more damage per round in two cases (glabrezu, death slaad), slightly more in one case (the mummy lord), slightly less in one case (the storm giant) and significantly less in one case (adult green dragon). I think the enhancement bonus does just fine when compared to elemental damage.