An avenger pursuing total dpf should consider physical damage as well as elemental damage. Thus Fortitude and mighty mercenary will be considered.
What is vengeance? Just plenty of enhanced elemental damage. This elemental ED could be added with physical non-weapon ED. The difference between elemental ED and physical ED arise from resistances of monsters, since under conviction and decrepify monsters will have typical elemental resistances -100 and damage resistance 0. So we can assume that elemental damage will has a double effect.

To get the best gears for an avenger, there're many items should be compared. For instance, COA vs Nightwing, Fortitude vs jeweler's AP of the whale(and the pattern of embedding). And a mighty mercenary holding the Reaper's Toll will be compared with a rogue with a Faith in hand.

Grand charms need to be selected too. One level of combat skills is compared with 10 maximum damage. Note that one level of vengeance will bring 18% total elemental ED.

Advantage of physical damage is that, it will reinforce the leech, to avoid exhaustion of mana.

In our calculation, elemental damage will be doubled because of resistances of monsters, and physical damage will be multiplied by 1.37 because of Highlord's wrath.

The process of calculation will be exhibited here, and I will only show some conclusion.
1.If we only get an attack speed of 9fpa, an avenger wearing Fortitude will get a total damage about 250 per hit less than that that wearing a jeweler's AP of the whale.
2.The highest dpf will be reached when the attack speed is 8fpa(only when a jeweler's AP of the whale is worn).
3.Avenger wearing Fortitude will balance the mana used in one hit in most cases(with the assumption that monsters in hell have typical drain effectiveness 50 or 75).
In my style, I'll prefer to wear Fortitude and COA, to get an attack speed of 9fpa, and to hire a mighty mercenary holding the Reaper's Toll.