The new Arcane missiles spell has a 40% chance to procc when you cast an offensive spell.
This is not entirely true.
It can procc from Remove curse. This could be usefull if you want an guaranteed Arcane Missiles procc before you engage a boss or whatever to get some more dmg.
Easy to do, just spam the spell on a target, and since the patch you can cast it even though you don't have any curse on you. And then it proccs.
Over and out!