The tanks in my guild (including me) having problems figuring this mechanic out. If anyone knows how this mechanic exactly works i would really appreciate if you share.
IIRC from 2007 if the Flame is taken more than 25 yards away from a warglaive it will charge and enrage, and if anyone is more than 25 yards from a warglaive it will also charge and enrage. I believe being within 25 yards of either warglaive places a hidden aura on you that makes you unable to be charged.
That's just what I remember from progressing in the ancient days it could be slightly different.