Guns are mostly useless against zombies. Humans hoever die to a single headshot 99% of the time, so that's helpful, especially when the alternative is charging a shooting opponent.

Suiciders are easy to kill with pistols, and killing them at range is a good idea, since they explode killing anybody in a couple meter radius.

Shotgun headshots are instant kills against **anything**, making them useful against special zombies. You may find [ammo blueprints][1], making firearms more viable. There are also repeatable quests that reward some ammo: [rifle ammo][2].

Bottomline: guns are situationally useful, melee is still the workhorse of the game. Purna's skills may remedy this somewhat, but other characters are perfectly capable of using firearms effectively, making her a poor choice.

PROTIP: dropping a gun will empty its clip into your ammo pool, so you can benefit from picking up and dropping subpar firearms.


  [1]: http://deadisland.wikia.com/wiki/Ammunition
  [2]: http://deadisland.wikia.com/wiki/Feeding_the_Multitude