Is there any use for the blighted armour/weapons in Warhammer 40k: Dawn of War II
These weapons are removing corruption from the squad wearing it, in Chaos Rising. You have negative stats, to prove that you are worth, and pure to the eyes of the Emperor.
However, if I remember good, such items are appearing also in Dawn of War 2, without the expansion. The "purification" bonus is not shown then, you will see it only if you finish the campaign and use this save in Chaos Rising.