Assuming your reflexes allow you to cast VT/SW:P on boss with room for a 3rd cast and you have less than 3 orbs
1) DP on boss with 2 orbs?
2) DP on boss with 1 orb?
3) Casacde/Halo/Mind Seer to Pad numbers?
Secondary question: Will the 100% proc rate apply to every new hop of cascade as it bounces around after Perfect Aim has run out? Easy to test out when I get home, but I am curious right now!