Which weapon damage mod is best?

Vs. Hexed foes
While Hexed
While Enchanted
Vs. All

If you cant afford a Vs. All weapon whats the next best thing?

+20% (while heath over 50%) or for my ranger (while in a stance)
+20% (while enchanted) is great if you use alot of enchantments
All the other Vs 'type" are not so good, but out of those I like the Undead, skeletons, Dwarves

Depends on the character. Generally, "while health over 50%" seems to be the most popular, but then again, maybe not so much for certain necromancers. It really depends on the character.

aye, any others?

http://www.gwonline.net/page.php?p=125

You should find that link very helpful regarding weapon upgrades. Seems very thorough.