The build above is a good recommendation.
On a lower budget, nightwing +15ias jewel can do the job too.
If you struggle with your fire res you can put FF on merc.
What you want the most :
100% pierce
-cold res
+skills
Your attack speed is secondary.
That build is kinda mana hungry…
Using faith you would have faster mana consumption for less dps overall.
Enigma helps a lot.
Your positioning can greatly impact your dps.
Piercing through multiple targets is not only making you deal your cold dmg to each of them, it triggers the explosion from each pierced target and is exponentially damaging all mobs in the radius of those multiple explosions.
More mobs = more dmg.
So you don’t have to shoot as soon as you see something…
Tele past them, lure them into lines, group packs, etc.
At some point very few arrows will kill them all. Your dmg is mediocre if you try to kill low density.
If you have some mana leech, using a might merc will help leech more. You can use strafe from time to time to fully replenish your pool. Else you’ll need lots of +MaeK.
If you don’t rely on leech, then defiance merc is best (you already have holy freeze from Ice)
D2:R