Hammer/Shotgun dungeon dps

Primary weapon: Hammer
Secondary weapon: Shotgun

Basic ability: Hammer / Smash

Active Abilities

1: Hammer | Shell Salvage
2: Hammer | Seethe
3: Hammer | Eruption
4: Shotgun | Raging Shot
5: Hammer | Demolish

Passive Abilities

1: Hammer / Obliterate
2: Hammer / Point Blank Shot
3: Hammer / Outrage
4: Hammer / Salvage Expert
5: Hammer / Annihilate

The basic idea of this build is to get off as many power abilities as possible. Seethe with passive also helps boosting your rage. Also notice that Salvage Expert will give you 5 hammer resources. The simple rotation for a beginner is to unload all energy and pop Seethe and Shell salvage for more. Spam Smash until you have energy for more power abilities. Doing some additional management of your rage will improve the damage output such as hitting Eruption when enraged, but this may also depend on signets and weapon.

It takes a bit of time to get the rotation perfect, but even when not caring too much about the rage mechanic this build works great.

Generally I like the idea (and this is almost identical to my current main DPS build) but I have a simple change which increases the DPS output of this build by a margin.

Point Blank Shot could look like a nice passive to have, but the DPS source of a Hammer main build isn't the direct damage of your offhand attack. I use Shotgun for its Dragon Breath stacks (as most Shotgun main and secondary users do) and focus on furthering my Hammer based dps with using Fast and Furious instead. Fast and Furious doesn't only give you a 9% damage bonus, but also grants speed increase by 25% for 3.5 seconds, which makes it easier to tackle moving targets without the need of an Alacrity affix. The idea is basically building up and keeping a 6 stack Dragon Breath damage over time while burning down Hammer energy whenever available. (minding when we have a full Rage meter also helps with more damage since we have Fast and Furious)

The same "Apply more burn to already burnt area while managing rage and burning energy with Hammer" idea can be implemented with other secondary weapons too. Assault Rifle and Elementalism Focus are the ones I have so far tried and enjoyed (especially with Orochi Thermal Inverter, Elementalism Focus becomes a great secondary weapon)

Also, I realized that you haven't given specific weapons that would optimize the use of this build. I hope my recommendations would be okay here.
Hammer(main weapon): Pneumatic Maul (obviously)
Shotgun secondary: SPES is a popular choice, but it tends to perform better while primary than secondary, since Ifritian Despoiler can be seen as a better option to further buff those Hammer attacks while still keeping almost the same amount of Damage Over Time from Dragon Breath shells
Elementalism Focus secondary: Orochi Thermal Inverter (which works wonders with Crystallized Flame and Flash Freeze w/ Blaze passive)
Assault Rifle secondary: I use KSR but that's because I'm a lazy slacker. Don't mind me, use MIRV or High Yield Launcher, which will give more time to fiddle with Hammer attacks, ease the tension of the rotation a bit and also have increased damage(to be used with Burst Fire and Incendiary Grenade, with Slow Burn passive for increased duration on your grenade damage over times)

Anyway, it's late for me, hope this recommendation actually helps <3