Guns vs Staff

[Instanthumor]

There are two different aspects:
1) Damage stat from a Staff is higher than the damage stat of a Gun; which makes the skill damage from equipping a Staff higher than a Gun.
2) The auto attack damage of Gun is higher than the Staff but that is a counter for the spread damage from the auto attack of a staff.

You also have to take into consideration that guns have a significantly longer range than staffs do.