I have taken a close look at the most changes in 5.4 and if no changes are being done anymore as it is now, frost DK's will absolutely dominate everything in PvP. As in be completely unstoppable and unkillable while doing tons of damage.
I will list all the things and then explain further:
Glyph of Pillar of Frost now reduces movement speed by 70% instead of freezing the Death Knight in place.http://ptr.wowhead.com/item=102298/e...akras#commentsGlyph of Regenerative Magic: If Anti-Magic Shell expires after its full duration, cooldown for the ability is reduced based on the amount of damage absorbed.
Pillar of frost has a 20 second duration with a 1 minute cooldown. If you use it on cooldown it'll be active extremely often. With the new glyphs you are not able to be stopped by any form of CC for whopping 20 seconds. We will be penalized with a 70% slow but then we have death's advance, also freedom might work(Frost TSG back?)
Now with the trinket I linked Pillar of Frost will have a 37 second cooldown while being on a 20 second duration. This means if you use it whenever it is ready you will have only 17 seconds without it. You can use desecreated ground/lichborne or icebound fortitude to prevent being vulnerable to CC's in this time aswell. This means a DK will N-E-V-E-R be able to get affected by any form of crowd control anymore in PvP.
Now we come to a huge thing with frost DK's which is their survivability, being immune to all CC's for permanent is already a huge buff to their biggest disadvantage(being squishy)
Now ontop of this the trinket also affects AMS it'll be on a 28 second cooldown and with the new glyph that is added AMS cooldown will under the best circumstances (AMS on chaosbolt/shatter) be reduced to a 14 second cooldown! while having a 5 second uptime if not destroyed. This means you can literally use AMS every 9 seconds.
Just think about us running trough arena, demolishing everything with 120k obliterates while not affected by any CC ever, completely unpeelable and immune to die vs (atleast) casters.
That's what I predict atleast. If my information is outdated let me know.