My last Doom/Dark Father experience:
I had a conjurer's trinket and two bows, a demon slayer heavy crossbow and a mischief maker.
I would hit the Dark Father with double damage from the demon slayer, and two hit kill lich lords with the double damage from the crossbow combined with the trinket. When too many rotting corpses showed up, I would switch to the mischief maker and do 200% damage from the undead slayer combined with the trinket. I hit max damage from my 100% from-items damage increase (thus 300% total) and didn't even have to switch my Enemy of One away from the Dark Father.