Not only that, but you will most likely have a 0.5-1.25 sec window in bethween Frost bomb coming off cooldown, and recasting it, and with NT while the window is same, as its from 2nd to last tick till recast, so the window of there not being a dot on is much smaller, and doing it every 12 secs with arcane and every 8 or so secs with frostbomb.. that account to quite some damage in the end..