RG Live WotLK 3.3.5a

In the actual version of this trinket, it ain't true. Although everyone (in the party/raid or not) gets the buff while standing in the circle, only the caster himself actually profit from the spell damage gain. As of 2.4.2, this trinket does now only profit the caster. He still has to stand in the circle to profit from the 320 spell damage bonus (although the buff last abit if you moove out of the circle), the cooldown has been reduced to 1:30, doesn't stack with other trinkets such as Skull of Gul'dan.