Well weapons are judged on how good they are in single player. Even though the Lance is technically the best weapon in the game, a team of four lancers would be odd to work with. Even with a tier list of weapons there still needs to be some team formation consideration.
The tier list I saw has
Lance
Hammer
Long Sword
Switch Axe (Axe)
Great Sword
Switch Axe (Sword)
H. Bowgun
Sword and Shield
M. Bowgun
L. Bowgun
Now tier list don't mean as much in PvE games. They are just meant to show which weapon allows one to win faster, easier, and more efficiently.
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