So here's my thoughts on Frost Bomb, the extra GCD/cast to get Frost Bomb going just isn't worth it. Not even regarding damage, the utility that arctic gale gives over frost bomb vastly outweighs frost bomb's benefit. Also here's some simsA quick note on Frost Bomb: I've been running this for the last week (Bracers with Soul of the Archmage, thanks to op) and found it to vastly outperform Arctic Gale. My overall DPS throughout the dungeons went up considerably, maybe someone could confirm my findings.
The sequence Frost Bomb>Frozen Orb>Blizzard>IL does crazy amounts of AOE damage, helps to focus down the priority target and gives you the same orb reset time. Frost Bomb will be up for the entire duration of T20 2pc and Soul of the Archmage will give you more than enough procs to pull ahead of Arctic Gale.
Plus, and that's what I like most I think, you get to press an extra button!
5 min test, 5 targets