Hmm. Interesting, though the last time I played my mages as frost (2.2 patch) even with 4 frostbolts going off at the same time it would break on the first crit. That's basically milliseconds apart, so I don't see how this works unless it's on the PTR and they've changed something.

[edit] And really, with a sample size of one duel, I'm not exactly convinced. :P