Here are my initial testing on 7.3 Frost DK, Obliteration built. Note that I am using Helm and Legs legendaries. I have not yet gotten my Chest/waist/wrist, which are more optimized for this built

My Talents.

56: RA
57: FF. ME could be better but currently I am using Helm Legendary so I am sticking with FF.
58: Icecap/Avalanche
60: Winter is Cominh
75: Inexorable assault
90: Gathering Storm
100: Obliteration

Rotation is the key here.
Assuming there is Bloodlust start, this is what you want to do.

Pop potions + Pillar of Frost

Remorseless Winter => HB => 2 x Obliterate (consume any Rime Procs) => Empowered Rune Weapon => 3 x Obliterate (Frost strike once in between in order not to over cap on Runic Power and consume any Rime proc.)

By this time, you should have 10 stacks of Gathering Storm dishing out major damage, and your runic power bar should be full. Use Frost strike + Obliterate to get your self to about 40 Runic Power and 2-3 Runes. This is important. Cast Obliteration.

Alternate between Frost Strike (Rime HB) and Obliterate. With 1 rune Obliterate and depending on the number of Rime Procs, by the time Obliteration ends, you should be back up to 5-6 Runes and near-full Runic Power.

It is important to cramp all these into the 20sec Pillar of Frost window as much as you can. If you have 2p ToS set, you have slightly bigger window due to extended Pillar. It is paramount to line these up with any Haste (trinket or mark of claw) proc/Bloodlust. Thus you also need a good amount of haste to ensure this. Currently I am sitting on 27% which seems ok.

Currently I am at ilvl924, I am able to dish out 1.3mil dps on Single Target. This is without my BIS legendaries for this built. It takes a bit of practice to get all the buttons down. I can top dps meter in most mythic/tos raid with proper execution.

Let me know if you folks have other suggestion on 7.3 Frost DK.

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Additional Discussion..

Shattering Strike
Without BoS, most of your Runic power will be spent on Frost Strike (and an occasional Death Strike), Shattering Strike might be viable as well. However RA does make make this built much smoother as you will not have awkward moment where you are sitting on 23 Runic Power but waiting 3 seconds for your rune to comes off cooldown.


Obliteration
This talent now last 10secs and allow HB to trigger KM as well. While this buff is huge with us no longer having to feel bad wasting Rime procs, there is a secondary benefit to Obliteration that is unwritten. Obliteration make Obliterate cost only 1 rune instead of the usual 2.

Every Frost Strike, have 25% chance (Runic Empowerment) to make your Obliterate free of charge. Each obliterate will restore 10 Runic Power. Now combine that with RA, ME and Rime procs, you can effectively cast Obliteration in a very rune/RunicPower starved situation (2-3 runes with 30-40 RP). Obliteration allows you to sustain good dps from a Rune starved position for 10 seconds. After Obliteration ends, depending of the number of ME/Rime procs you get during Obliteration, you will more often than not be at full runes. This means that you if you see that your Obliteration is coming off cooldown, you should spam out all your runes/runic power to ensure no runes are wasted during Obliteration.

Use Obliteration not only as a dps cooldown, but also a way to "restore" rune.