Of course the Glyph is used. Your gear and raid buffs provide you more than 20% haste, right? and lust is 30%, plus Troll's racial ability, it's more than 70%. The GCD cap is 50%
The issue is that Haste is not additive
; it's multiplicative
. And, which Soft Haste Cap are you referring to? Are you looking into the one where Frostbolt falls under the GCD, or the cap where the GCD reaches 1 second? Because the GCD being at 1 second is fine, as long as most of our casts remain above 1 second.
I'll use the Haste from my gear as an example in the following calculation (I'll ignore Frost Armor for now, since I'm not sure if it's multiplied, or if it literally increases all your Haste in the end by 5%):
1.05 (raid Haste buff) * 1.20 (Berserking) * 1.30 (Bloodlust/Timewarp) *1.1326 (Haste from my gear) = 1.8551988 = 85.51988% Haste (not sure how Blizzard would round/truncate this value, so I'll leave it as is).
The total Haste needed for Frostbolt to reach a 1.0 second cast time is:
Base Cast time (2 seconds)/Desired Cast Time (1 second cast time) = 2 =100% Haste, so more gear is needed for Frostbolt to become an issue, and even more gear is needed for those who don't have Troll as their race.
As for Mage bomb, that ultimately depends on which bomb you're using (bombs are considered for all specs). Under these conditions, Frost Bomb definetely falls under the GCD, Living Bomb has a 1.0 seconds GCD regardless of Haste, and since NT is an instant, I don't think it's affected. Ice Lance and Frostfire Bolt, when used with Brain Freeze, wouldn't be affected either.