Hexan or Warlock
The Human Summoner class is characterised as the easiest to use of the three summoning classes because of the natural decent Human physical statistics of CON DEX and STR.
Summoners in General
The three summoner classes have hardly any differences except for their summons themselves. For the Human Warlock the summons take the form of various Cats. Which generally are easy to use because of their decent damage and toughness that have additional basic (though relatively weak and useless) offensive spells (Mega Storm Strike). Also like all the summoners the Human Warlock has access to cubics. Also all summoners have a variety of support spells for their servitors. An integral spell of the summoners is the Transfer Pain spell which transfer missing hp from the Warlock to the Servitor, which he or she can heal.
Warlock Pros and Cons
The damage of human warlocks come from three sources. The summon, the cubics (the storm cubic), and the warlock himself. The cubics however have poor range. Usually they take action in melee range. (Though some people say that they have roughly 300 - 400 units of range.) So the usual tactics for summoners are to get hard hitting melee weapons. And as melee combatants their decent CON provides better survivability.
The only problem will be most likely the lack of movespeed which can give problems when it comes to sticky situations. Though this can be remedied with items like potions.