I'm not 100% sure but it appears they are using Bigwigs and have Allure of Flames Emphasized. You can set that up in bigwigs with these steps.
/bw
Click Bosses
Click Hellfire Citadel
Select Archimonde from the drop down menu
Scroll down to General and click >> for Allure of Flames
Check the box for Emphasize.
You can also check Countdown for a verbal countdown of this as well
Allure of Flames occurs 30 seconds into the fight and roughly 1 minute after the first one. I'm not well versed in writing weak auras, so not sure how to go about writing one for that. Like I said earlier, here is my WA for Allure of Flames that shows up once he starts casting it.
Code:
dCd6daGEqPDPGEnOyMsOMRcmBLUjLsUTuTtczVODtX(fQ(PuQ(Ru8BOgkLsnyrvdxroOq6ys0HjAHeQLcQklwuA5cEOqjpv1JPKNdzIukyQsAYImDQUfOkUQqPUmPRdYgffptkPnRO2oOY6avPVcQQMMuIVlbJKsrNgy0uQgMqCsrLZsPqxtkLZRqFMGLjumojKzjR8D(eFIvEPLdWgeR8ixgCw57kcjfuE(eUryXfyw(eUPRiKuqzw(eUbHHmjMLVRiKuqB8XjL)rTrEHfxOrA5aSHhzhxGhHHmj(CgxdZslDq0uQDdAGTdshEADyKbhdzsObfdmWmeliWlS4cnZbzx5HFvctuOGebVrdoyxnmsNoV0a6shGnSYJCzWzLFkOi15rtGGCPtN3dabbnWkVpoP8kCQX5rt6U5s8Lf1AmT1cpKrHtnoVd6AIpPzHMNRJtkVnJcF2ktSlMpbfKoaB4BHxHtnoFSW9SspE(IXc8qiTbnP7MlrX8OjD3CjeRuujfvwumLrkIoVr2veRuujF0Gd2vdJ05nYUYhDxOGgppEoE(mRSRi(zODrwsdfZBbHCCVXoiP8oORj682vGGDNIkJeHFXYeR8qiTXOWPbML3LRACw57qRdyLoD(eyEgybT(iR8iGryv((OBhyX3HwhWkFF0TdSOyE7AadSOyEdo0LlftNoFqAPSY3HwhWkD68b8QSY3HwhWkD68qiTbwSrPyEyXgL3M6UZGGgpFSaUmPlpcaRYkFhADaR8Eb14JumD605NXg)ayvkQSn(eanTYX7slyq82aojOXZNbeu(GkaWM64KYdSWgEKlTGbzBmW48IBVwB3w8WIXDkkYWw5LqoMz5bj(O7cf045XZXZNzLDfXxaKC7uuzKi8gOEnaee0aIIk5LPeWbyJCB8aqqqdiwPZNaOPvoMZcB4ZzCnmlT0b5SWg0GpP72Kbe0Mm6MzLD9EaaJYBHXBcxWqX05r8XmSCyKHTXdhfv2smL0jb