My hammerdins equipment:

Helm: Shako
Armor: Enigma
Ammy: Rare +2 combat skills, 10% FCR, and some fire and light resists
Weapon: Wiz Spike
Shield: HOZ
Belt: Arachs
Gloves: Frosties
Boots: Eth Sandstorm Treks
Rings: BK ring, SOJ
Charms: Gheeds, Anni, Bunch of life charms (I have no combat skills charms)

I’m pretty sure my hammer damage is around 7.5k per hammer. I have heard of people getting 12k per with HOTO but I don’t have one so I just make do. As it is now I don’t think I really need one. I have 75 resists all in hell and about 1500 hp. I can cast hammers for about 1 minute non stop before I run out of mana. Then a quick switch to redemption fills my mana and life bulbs instantly. My hammerdin is incredibly durable. I often tele into mobs of monsters in Chaos Sanc and spam my hammers. My HP bulb maybe drops to halfway after the 2nd or 3rd mob, but then all I have to do is switch to redemption and its full again.

The monster that is immune to hammers is because he has the properties of magic immune and at the same time he is NOT undead. It is some kind of bear thingy. I never go through act3 so I don’t ever see them.