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Flexible Raid (also called Flex) is a raid system integrated into Raid Finder, Normal, and Heroic modes. It allows for raid content to automatically scale its difficulty depending on how many players are in the raid at the time the bosses are encountered—between 10 and 30 players. That means if a raid has 11, 14, or 23 other people available for a Raid, they'll all be able to participate, and the enemies will scale dynamically.[1] This difficulty scaling will bottom out at 10 players, even if you have fewer than that in the raid.

Raids using the Flex system operate on a loot-based lockout, allowing players to fight bosses they had already killed (but without subsequent loot).

World bosses also use this system to scale their difficulty.


Flexible Raid UI

The pre-6.0.2 Flexible Raid UI

In Patch 5.4.0, Flexible Raid was added as a separate difficulty that sat between Raid Finder and Normal difficulty (now Heroic) that was available for premade groups of 10 to 25 players, including any number in between. It was entered via queueing through the Flexible Raid UI and was separated by wings, similar to Raid Finder. It required a minimum of 8 players to queue. This difficulty was only available for Siege of Orgrimmar.

In Patch 6.0.2, the Flexible Raid difficulty was renamed Normal and this flexible scaling system was applied to Raid Finder, Normal, and Heroic (old Normal) difficulties for Siege of Orgrimmar and all subsequent raids. Heroic was renamed Mythic and remains the only difficulty to not use this system—being statically tuned around 20 players.


There are generally no set breakpoints for boss abilities. With a few exceptions, each person in the raid adds a 20% chance for the boss ability to target an extra person or have an extra effect.

It's called flex for a reason... | 2013-12-10 01:38 | Blizzard Entertainment Ion Hazzikostas

At BlizzCon, we'd discussed some improvements to our Flexible scaling system that would minimize the existence and impact of any real or perceived "breakpoints." Our design goal has always been for the system to be neutral with respect to group size. Specifically, you should never feel encouraged to turn away interested players whose skill/gear level matches the rest of the group's, basic role composition constraints notwithstanding. But at the same time, you shouldn't feel like you need to go out and grab warm bodies if you have a perfectly serviceable raid already assembled. Clearly we have not yet fully realized those goals.

In general, the existing healing/damage scaling slightly favors larger groups, since boss health and damage scale up more slowly than does raid throughput. To use a specific example, an 18-player raid with 12 damage-dealers will kill a boss slightly faster than a 10-player raid with 6 damage-dealers (assuming equal skill/gear between the two groups). But it is true that currently some specific abilities exhibit breakpoints, where adding an extra player causes an extra add to spawn, or an ability to strike an additional target.

To help smooth out difficulty scaling as you add or remove players from your Flexible raid, we will be implementing one of our planned Warlords changes to the scaling system ahead of schedule. In the near future, several boss abilities that target more players as the size of a Flex raid increases will use weighted randomization rather than strict breakpoints.

An example to illustrate what I mean:

Today, Sun Tenderheart's Shadow Word: Bane ability afflicts 2 targets if your raid size is between 10 and 14, but begins to hit a third target at 15.

Once our upcoming change is in place, if you have a 13-player raid, there will be a 60% chance for each cast of the ability to hit 3 targets, and a 40% chance for it to hit 2. If you add an extra player, and thus have 14, there will now be an 80% chance for 3 debuffs to go out, and a 20% chance for only 2.

In short, with respect to this particular ability, adding an extra player will always give you an average of 0.2 extra Bane debuffs. No more breakpoints!

There will be a handful of exceptions where breakpoints remain necessary. Imprison on Sha of Pride is probably the most notable such example, where you really want to pre-plan who will cover which prisons, and having a random number of targets each cast would cause frustrating unpredictability.

There's nothing wrong with 14-player groups -- 14 players is a great size for a raid. But so is 15. And 19. And 12. And 22. We just want to help make sure that good players aren't being turned away from groups because of the notion that their presence will make things harder for everyone.

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In Normal and Heroic modes, the bosses available in the raid instance is determined by the raid leader's loot-based lockout (first unkilled boss). If the raid leader has already completed all the bosses in the raid, it will start at the first boss.

I completely misunderstood Flex raiding | 2013-09-13 20:04 | Blizzard Entertainment Crithto

Once again, this community has come together in a constructive manner to share feedback and suggestions, and we thank you for that. Let's kick this update off with the most recent change:

After careful consideration of the feedback you've shared, and after weighing pros and cons of the Flex mode system that came with Patch 5.4, we've decided to change how raid progress is saved. At patch launch, entering Flex mode SoO was based upon who had progressed the least. For example, a raid of 11 players entered SoO and downed 3 bosses on Tuesday night. Wednesday night, all 11 come back together to continue but decide to bring along 4 new people. If the raid had queued together, they'd have had to start the raid over from the beginning because those 4 new players weren't flagged as having downed the first 3 bosses. Our original intent was to err on the side of making sure no one in the raid would miss out on a boss that they still needed to kill.

A hotfix applied this morning, however, takes a more traditional approach to raid lockouts by basing boss progression on the group leader's status. In other words, if the raid leader faced 3 bosses on Tuesday and decides to continue where he or she left off tonight, anyone who joins the Flex raid--even those who have never set foot into SoO--will begin the instance at the same point where the raid leader finished on Tuesday. This system is more straightforward and understandable for much of the WoW raiding community, therefore Flexible raids will no longer be based upon the least progressed member.

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I completely misunderstood Flex raiding | 2013-09-12 19:15 | Blizzard Entertainment Crithto

There has been some confusion about a couple aspects of Flexible mode raiding which we’re hoping to clarify for you here:
  • If all members of a Flexible mode raid have killed specific bosses within a wing, when they queue up again the next day, they will begin where they left off.
    • Example: All 14 players in the raid on day one have defeated Immerseus, but only 12 continued on to take down the Fallen Protectors. If that same group of 14 were to re-queue for the same wing the following day, they would begin at the Protectors with Immerseus remaining defeated. If they returned with the original 12 that downed the first two bosses, they’d carry on to Norushen.
  • While Flexible mode will never scale in difficultly below 10 players, you can still queue up and begin clearing the instance with as few as 7 players in the raid.
    • Example: You have 9 guild members and friends who are online and ready to rock Flexible mode, but the other 5 members of the raid are running a bit behind. You can still form a raid group and queue for Flexible Siege of Orgrimmar, and then head inside to begin taking down trash as you wait for the others to log in.

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See also[]

Patch changes[]

  • Mists of Pandaria Hotfix (2013-09-13): Boss progress lockouts now based off of the raid leader's status.
  • Mists of Pandaria Patch 5.4.0 (2013-09-10): Added.


External links[]