This morning Blizzard posted a news blog announcing a new feature to World of Warcraft. This new Flexible Raiding gives players the option to take raid team between 10-25 and have the raid auto-scale appropriately to the number of raid party members.
Also in this feature is the ability to use battle tags for cross-realm raiding! Don’t have enough for a 25 man on your server? Bring your battle tag buddies along!
/Flex will use the LFR style loot system so that each individual will get a chance at loot, as well as it will have a separate lockout than LFR or Normal/Heroic raids. Giving you the opportunity to participate in all three.
Players will see loot gear levels between that of LFR and Normal. Adding a new tier of Item level to the game. This gives casual raiders a new option to raid. If you don’t have enough for a 25 man raid, but more than enough for a 10 man, /Flex raiding will allow you to take your whole raid team in for the fun.
For More information refer to the Blizzard post listed in source below.
Source: Blizzard Blog