POB:https://pastebin.com/SWAB7NUc

If you've league started dominating blow and have run into a brick wall in trying to scale DPS without costing you valuable EHP stats here's a couple of my findings:

1. Cold Conversion scales much better than Physical as the impale support gem is no longer as much of a damage multiplier it used to be (it's also mandatory since you can't get impale chance on your minions otherwise. There's also no good sources of physical penetration or resistance shred for your minions so there's that as well. While for Cold Conversion you have Elemental Army and Elemental Equilibrium.
2. Dominating Blow's scaling on Gem levels seems to mimic that of Herald of Purity's with a 13% increase per level. This means that getting + levels on your 6L should be one of your priorities once you've overcapped resistances on the rest of your gear, one way of doing this cheaply is with a tabula, another is with a Skin of the Loyal with decent corruptions. This also means one of the strongest support gems for it is Empower 3 or 4. A Tabula with +1 all gems implicit with an Empower 3 gives you effectively 21+1+2+1 = 25 total gem levels on Dominating Blow.
3. If you're doing a full cold convert to triad, dropping Herald of Purity for Skitterbots is almost mandatory. The extra chill effect when linked with bonechill and unbound ailments as well as the extra damage taken by enemies from bonechill and shock effect is very substantial.
4. If you're chaos capped, Forbidden Taste flask + savage hit enchant is one of the most broken defensive layers present in the game right now, as long as you have flask charges up and the hit taken won't outright one shot you, you're not going to die. Overflowing Chalice + Increased effect enchant's sole purpose is to keep uptime of Forbidden Taste flask charges.
5. Animate guardian is one of the best summons you can have, but its a pity it dies so much in boss encounters.
6. Behead gem gives amazing QOL with its attack range, 25% more damage on average as well as your sentinels having the ability to steal buffs from enemies. It's 100% if you're just starting out mapping and works really well with Melee Splash in giving you a pretty zoom zoom playstyle.
7. Forget about alt quality versions of Dominating Blow, as its skill levels grant 13% more per level getting a 21/20 or even a 21/0 gem is way better and cheaper than any other alternative.
8. Whakatutuki No Matua and Hatred linked with Generosity is one of the cheapest ways of scaling Hatred aura for your Sentinels, granting 79% aura effect with minimal investment.

If there's any question on Dominating Blow that you need answered I'll try my best to answer them here. Do note, it's my first time running this skill and this ascendancy so some of my assumptions may be wrong.