Here’s a link to your seasonal DH…
With that in mind…
However, immediate things I noticed…
Amulet - you want a Hellfire Amulet or Squirt’s Necklace
Bracers - you want Wraps of Clarity bracers for lots of mitigation
Legs - reroll Armour into Vitality
Quiver - missing +12 Discipline secondary affix
Bow - missing +12 Discipline secondary affix
The discipline is a major one as the UE set gives you 350% more damage for every point of discipline you have. So, by missing out on 24 discipline, you’re missing out on 8400% damage.
There’s also the possibility of including two pieces of the Captain Crimson crafted set (belt + legs or boots) and cubing a Ring of Royal Grandeur. The Crimson set gives you a lot of extra damage (from CDR) and mitigation (from RCR).
Also, you’ve runed Multishot with Full Broadside. Until you get to much higher GR levels, where it involves corralling large groups of mobs into packs, the physical rune isn’t the best choice. For smaller pack pulls, or where you’re still pretty much one or two shotting trash mobs, the fire rune Arsenal is better. Whichever rune you end up using though, your bracers should have CHC and 20% elemental bonus that matches the rune you’re using on MS.
Oh, and then there’s the stuff you have Cubed. You’re missing Dawn (65% CDR on Vengeance, which will allow you to keep 100% up-time on it) and Visage of Gunes (gives Vengeance the Dark Heart rune, which is 50% damage mitigation).
Oh, and Companion / Ferret. Unless you logged out after having done some gold-farming, that’s not a useful choice of rune. Usual choices are either Boar (for more mitigation) or wolf (for more damage).
As for Shadow Power, drop that and replace it with Preparation / Invigoration, as that permanently raises your max discipline by 20. Again, due to the UE set bonus, that’s 7000% damage.
So, quickest things are choice of skills / runes. Then, if you fix the discipline on bow, quiver and skill, you’ll gain 44 discipline, which is worth 15,400% damage. Some of the other gearing choices will also make huge amounts of difference to your mitigation / survivability.