that Winter Orb lol
just 1 base projectile? and gmp shotgun (270%more damage from gmp lvl20)
2.5sec casting gives 10stages and make the skill last for 4sec, and does 150%more damage then stage 1
asume you have 30%castspeed and 90%skill duration=====>1.92seconds of casting gives 10stages, lasting for 7.6seconds====>25%of time you need to cast for max dps