Word of Pain2

What is going on with this skill? The difference between me not putting word of pain on an enemy and when I do is night and day. Enemies get shredded once this is put on them my damage inflicted is nearly doubled. Is it actually the +Fire and Cold bonus from Word of Agony? That’s the only stat boost across all the links of WOP i can put my finger on.

It is good on trash mobs but against bosses not so much. It is also a good devotion proccer. I think that it is Death Sentence that adds the most damage of the three nods.