The timer is now the lengh of the spell lockout from the interrupt used. That is, he will cast Searing flames again as soon as he is able. Shamans (I think it's them, sorry if not) have a 3 sec interrupt ability. Basically, instruct people to not use any ability of this sort, as it will lead to chained casts and people still on CD.
But - what I would like to know from those in the know is whether the spell we need to interrupt is cast on a regular timer or not. Seemed to be about every 10 seconds or so BUT I swear there were several occassions where he appeared to cast the ability we needed to interrupt back to back i.e. i'd kick and a split second later he was casting it again. This did kinda mean anticipating the interrupts was tricky. Anyone know?