Prometheus Diablo Portal
Prometheus Diablo Portal
Firebird's Finery Bugs
Despite having played Diablo III since it's initial release in 2012, and having played the Wizard class several times, I never used the full Firebird's Finery set. Just before the start of Season 20, I tried out the new Typhon's Veil set which was introduced in Patch 2.6.8 and was planning to use it again for the duration of Season 20.  
 
Things did not go according to plan, and the random nature of the game led me to the direction of using Firebird's Finery for the very first time. I quickly adapted to the style of play required by the set.

The set bonuses for Firebird's Finery is as follows:

(2) Set: 
When you die, a meteor falls from the sky and revives you. This effect has a 60 second cooldown. 

(4) Set: 
Dealing Fire damage with one of your skills causes the enemy to take 1000% weapon damage as Fire per second for 3 seconds. This effect can be repeated a second and third time by different skills. If an enemy is burning due to three different skills simultaneously the enemy will Ignite, taking 3000% weapon damage per second until they die. 

(6) Set: 
Your damage is increased by 200% and damage taken reduced by 3% for each enemy that is Ignited. This effect can stack up to 20 times. You always receive the maximum bonus whenever a nearby Elite monster is Ignited.

After much grinding, I eventually managed to aquire 6 pieces of the set and was able to begin benefitting from the applied bonus. Soon, however, I discovered that a bug exists in the set and that not all Elite monsters within the game ar subject to the 6-piece bonus of 20 ignited stacks. 

There are essentially 4 types of Elites in Diablo III:
  • Champions
  • Rare Elites
  • Unique
  • Super Unique
For all intents and purposes, I consider Unique and Super Unique monsters to be differeniated only via the banner used in-game below their name on screen, of which there are two types:
"Bar" Monster Banner
"Marque" Monster Banner
According to Diablo Wiki, Super Unique Monsters are a type of Unique Monsters the difference between them being that the names and location of Unique Monsters are always random, while Super Uniques have a fixed name and spawn in the very same location in every game.

But regardless of their classification as Unique or Super Unique, at would appear that not all of them are subject to the 20-stacks bonus when your hero is equipped with 6 pieces of Firebird's Finery.

The following screenshots highlight this issue. Regardless of how many fire skills you use on them, the ignited stack does not jump to 20 as it should when using 6 pieces of Firebird's Finery:
As can clearly be seen in these screenshots, Firebirds Finery doesn't always apply the full 20 ignited stacks to Unique or Super Unique monsters. This can only be a bug in the system which should be addressed, as it completely defeats the purpose of the set. The 6-piece bonus descriptor does after all specify "You always receive the maximum bonus whenever a nearby Elite monster is Ignited."

The following screenshots show a series of Unique and Super Unique monsters to which the full 20 ignited stacks has been applied:
As was previously stated, Elite Monsters are classified as ChampionsRare ElitesUnique and Super Unique.
Diablo © Blizzard Entertainment, Inc. All rights reserved. 
All trademarks referenced herein are the properties of their respective owners.