Diablo 3: PTR 2.1 legendary set: Firebird's Finery

[update] 2.1 is now live! The set now works exactly the same as shown in this video.

Firebird six pieces bonus is significantly changed in PTR 2.1!
"Dealing Fire damage causes the enemy to take the same amount of damage over 3 seconds, stacking up to 3000% weapon damage as Fire per second
After reaching 3000% damage per second, the enemy will burn until they die"

When you hit a mob with fire damage, it gives a three seconds dot debuff to the mob. Further fire damage to the mob refreshes the duration of the debuff and, more importantly, add the damage to the debuff. Once the damage of the debuff reaches 3000% weapon damage per second, it continues to tick until the mob dies!