I agree but it isn't the case with the Greatsword (and probably many other weapons). One of the great benefits of going elemental is to troll PvP players who love to block. 200+ dmg through a shield is no joke lol. Here is the breakdown:
My Greatsword +10 with 40 STR I was doing 400base and ~150 from the scaling for a total of 550 DMG. With the flame buff I would do 50 fire and additional 30% fire dmg for a total of 615dmg.
Now the Flame Greatsword +10 I am doing 280phys, 280 fire with ~60 phys and 20 Fire from scaling = total 640 damage.
So at FIRE +10 we are already doing more damage than the physical build WITH buff. Now we add the buff
With the Flame Weapon buff, we add 50 fire dmg and 30% increase to fire damage. We are at 340 Phys and 455 Fire damage. For a total of 795 one handed damage

Like I said, it does 200DMG on block
PS. Screw the Crypt Blacksword -- I'll take longer range and less stamina consumption with equivalent damage.