You could use CBMT and create 12 yell timers (3 possible phase times * 4 seed spawns):
Create one timer each for each combination of the following:
Durations:Code:Enough! I will finish this. Fall to your knees, mortals! This ends now. Sulfuras will be your end.
Code:Seeds 1 - 15 sec Seeds 2 - 75.7 sec Seeds 3 - 136.6 sec Seeds 4 - 197.2 sec