Prior to 1.3, the Golem's Fist was an unlikely item. Rare drop with very few options to get it. However, since 1.3 (in beta), there appears to be a lot more chances to get it. It remains hard to get either way.
Midnight (not in list) is hands down the best option. Best DPS, plus the paralysis is brutal. However, that requires completing The Pit, often a harder task than beating the main quest. One can get it before the Ark. In fact, it can be part of collecting the Shards as one is found nearby. So it's technically a "pre-ark" weapon.
Of the options listed, the Paladin's Longsword works well. The three different minotaur types have different resistances so you can swap between weapons to try to sneak out a slightly better damage output, but the Paladin Sword is a good all-purpose choice.
If you Cleric has high Agility, and esp if using Battle Prayer or Might, than the faster Spirit Hammer can sneak in a little extra damage.
Final thought: Pick one and stick with it. Pick the weapon that gives you the highest DPS and use it. Trying to overthink the DPS argument can give you a headache with very little difference in game play.