Looks pretty good. The only thing I'd really change is the Hoarfrost slotting, it's much more valuable as a heal than as a mule for some weak set bonuses. If you can't find the slots to 6-slot it, you can just frankenslot it with the slots you already have using +5 Heal/Recharge IOs from three different sets.
Aside from that, you don't have any knockback protection, but you can get that by putting a Blessing of the Zephyr in Fly. Fly's capped for speed completely unslotted, so that Fly speed IO is doing nothing for you anyway. Or you could six-slot Overwhelming Force in Ice Bolt or Frost Breath, get the KB protection there, and put a Winter's Gift Unique in Fly.
Also, for Aim and Build Up, are you a stacker, or an alternater? If you like to alternate them, that slotting is good. But if you like to use them at the same time and stack them, the Chance for Build Up should go in Build Up.