2h vs Dual Wield, I don't think it makes a huge difference for frost. It is minor. Dual wield is less bursty but more constant damage. Killing machine will proc more often with dual wield, but each hit is smaller. 2h is a little better since you will be kited and when all your runes are available, you output more with 2h.

in short, when you are kited, you will be spamming HB. In this case, 2h = dual wield. Finally when you get to him, you have your runes and runic power. 2h > dual wield when you use all your runes + runic power.