The clicky Frigid Weave of Destruction adds damage at the end, after focuses and whatnot--not to base damage. It lasts 2 minutes or 20 casts (whichever comes first), and Twincast eats up 2 counters per cast. So the damage increase on this is locked to 160k total additional damage per use, IF you manage to get all 20 casts in.
Edited, Apr 29th 2013 11:23am by FlibFlop