Hi, so it starts with every class (except fighters?) has something in their enhancement trees to add some kind of damage effect, that is similar to the elemental damage that weapons will have (like 1d6 cold damage). As an Rogue, in my Assassin tree I can add poison. 1d4/1d6/1d8 levels of damage. So you always want to grab that.
Then, you can add imbue dice that are your multipliers, adding 1/2/3 additional dice to whatever your damage generator is.
So, if I go all 3 levels of poison, I add 1d8 of poison damage to any weapon I wield. Then if I add all the imbue dice, I am now adding 4d8 of poison damage to any weapon.
Then, since it has a large Melee multiplier, in higher levels when you have lots of Melee power, the damage continues to be significant.
Imbue dice are an important part of getting your DPS up.
I hope this helps.