Due to its damage boost offered to raid teams, Z'en's Redress has become a staple set whether it's on a support or DPS role.

Z'en's tooltip reads:

Your Light Attacks apply the Touch of Z'en on enemies for 20 seconds. Enemies with the Touch of Z'en take an additional 1% more damage for each damage over time effect you've placed on them, up to 5%. You can only receive the benefit from one Touch of Z'en per enemy.

As a note, Z'en's Redress offers the 5% damage taken on a target to EVERYONE in your group. This is usually put on a non-Warden healer or a Magicka Dragonknight DPS as of the Stonethorn patch.

So what constitutes as a Damage Over Time effect to fulfill the Z'en's Redress condition?

Skills
Soul Trap & both morphs
Entropy & both morphs
Swarm & both morphs
Cripple & both morphs
Lotus Fan
Trap Beast & both morphs
Sun Fire & both morphs
Searing Strikes & both morphs
Fiery Breath & both morphs
Burning Talons
Scalding Rune
Destructive Reach
Non-Skills (Chance)
Poisons (Creeping Ravage Health/Ravage Health)
Burning status effect DoT (Burning Embers)
Burning status effect DoT (Burning Talons)
Burning status effect DoT (Scalding Rune)
Burning status effect DoT (Inferno Staff)
Poisoned status effect DoT (Venomous Claw)