Have you guys ever hear of this strange cast, called Blizzard II? it basicaly does the same as Tri-Desaster but: it faster (2 sec cast), has a higher Potency (50 instead of 30) and cost just about half the MP.
ok, it also binds just about half as long but i've never had a situation where i prefered Tri-Desaster over Blizzard II (wich i can cross from the THM)
