Help me understand the scaling please.

Due to the way that grief's damage is a side stat of +340-400 damage, the %ED on a superior phase blade wouldn't really make a difference right? It would only effect the weapon's base one-handed damage of 31-35 on a phaseblade. (increasing it to 35.65-40.25)

0 diff if you're a smiter

it's another +4.5 dmg if youre not

Only if in zerker not pb

Correct, it is "ADDED Damage" to "Min / Max Damage" after other %modifiers been added.

Excluding certain skills as posted by others.

Example, the Berserk skill on a barb converts all damage to Magical, and if you had like 1000% enhanced damage;

The phase blade damage will be calculated separate from the Added damage and then added together.