Sad for someone like me that is actually playing frost 'correctly' right now though, since obliterate isn't actually worth casting at all right now, so buffing it is a large buff to the wrong playstyle. IE it's probably like a 5% buff in reality.
na it's massive for a few reasons and will net frost dk's that change their playstyle much much more than 5% (afaik the runic attenuation ignore frostscythe build was already very very close and competitive with the frostcythe 'correct' build)
1) The new "correct" way to play frost will be to ignore Frostscythe and go Runic Attenuation.
2) Frozen Pulse is being reworked to have nearly double the uptime as it did before at the cost of a small damage decrease (but massive overall damage increase due to uptime).
3) The howling blast and obliterate buffs are just massive, nearly 30% for the former and 20% for the latter -- so even "losing" Frostscythe you gain immense single target through runic attenuation and the raw obliterate buff, and frozen pulse is godly for AoE along with the new howling blast and remorseless winter.
Not even mentioning the rune of razorice change yet which is just a straight up 5% buff to frost damage which is like 60-75% of a DK's damage. These changes also put more value on the belt/helm legs which is pretty nice for people that have those (while the bracers remain godlike). So Frost DK's have 3-4 legitimately strong legendaries (more than most specs).
Massive buffs across the board for Frost, and I honestly think it will surpass Unholy. Will be one of the best melee classes for mythic+ because of the really strong sustained AoE, godlike cleave, decent ST now, and it comes with a brez. Really exciting time for Frost DK mains, Blizzard doesn't usually buff on this massive scale, but this time they actually did and it's going to elevate a weak spec into a very solid position (and they should do this more often when it comes to these lagging specs, the incremental 3-8% buffs once every month or two really does nothing for a spec at the bottom).
Frost will always have scaling issues with the way killing machine works, but I mean if they keep hitting it with large buffs with the introduction of every raid, that doesn't really matter.