I honestly couldn't find anything about this. At which haste rating do frost mages benifit from Glyph of Icy Veins. It is of course when your cast time on Frostbolt drops below GCD.
At the moment my mage has 7377 haste rating, that is to 17,36% unbuffed.
But during a Time Warp you want to be able to use Icy Veins. So with moonkin aura it should be like this:
1.1736 (my haste) * 1.07 (frost armor) * 1.05 (moonkin aura) * 1.20 (icy veins) * 1.30 (time warp) = 2.056921776
So during Time Warp and Icy Veins my haste percent would be 105,69% which brings the cast time of my Frostbolt would be ~0.97 sec, which obviously is too low since lowest GCD you could achieve is 1 sec. The perfect cast time would be 1 sec and you reach that with 100% haste since base cast time is 2 sec.
So for 1% haste is 425 haste rating. This would be the correct calculation to obtain the required haste rating to obtain 100% haste with Frost Armor, Moonkin aura, Icy Veins and Time Warp.
X (my haste)* 1.07 (frost armor) * 1.05 (moonkin aura) * 1.20 (icy veins) * 1.30 (time warp) = 2
1.07 (frost armor) * 1.05 (moonkin aura) * 1.20 (icy veins) * 1.30 (time warp) = 1.75266
2 / 1.75266 = 1,141122636449739 = 14.1122636449739%
14,1122636449739% * 425 (1% haste) = 5997,7 ~ 5998 haste rating.
TL;DR: At 5998 haste rating your Frostbolt will have a 1 sec cast time with Frost Armor and Moonkin Aura during Icy Veins and Time Warp.
Please correct me if I'm wrong.
Do someone have calculations on which haste rating it is benificial to use Glyph of Icy veins?