There's something about MMOs that just says "we need 4 versatile classes to make for a jolly good time.

Those 4 classes obviously being along the lines of:
Warrior
Mage
Archer
Rogue

Pocket legends is a great game and has done so much in such a short time although the game is missing one dire roll or class in the MMORPG scene.....

The Rogue/Assassin archetype.
Roll: In most cases this class would be a high burst DPS class (like the Avian Archer) but more of a mid to melee range, and focusing on Crit rating over Hit.
Weapons: Claws/Daggers would be the weapon of choice (possibly duel-wield), and maybe throwing stars/knives for a mid range attack.
Equips: concealing ninja-esque attire with incredibly low armor.
Attributes: Rogue or Assassin would usually be a stealth type class meaning high dodge or avoidability to make up for the low armor.
DEX could be a good stat for this class but the best bet would be to make a new stat
LUK-Luck: A stat common to the rogue class in maplestory, ghost online, and wonderking.
Or
AGI-Agility: A stat equivilent to LUK in most of the 3D MMOs.

Example in Pocket Legends context:

Agility (or Luck): Increases your crit and dodge chance

Animal archetype: So every class seems to have a coinciding creature that goes hand in hand with the class
the ursan bear warrior
elven enchantress
avian (eagle) archer
So, what animal would a rogue be? There are 3 I can think of.
Fox
Racoon
or Badger.