[Kyrottimus]

Having played every class, this is how I rate them as the most frustrating to the least frustrating to play (in war):

In a scale--
Most Frustrating

Barbarian: Reason -- Mana-hungry. CC'd to the point of unplayability. Heavily targeted. Resists/Evades making the risks of charging almost not worth it and destroys fun.
Knight: Reason -- Too little damage, slow, blocking unreliable and unpredictable.
Conjurer: Reason -- Hard to target allies, heavily targeted. Plusses, allied heals/mana/buffs NEVER get resisted.
Marksman: Reason -- Not versatile enough, but good mix of range and damage. Still, too mana-hungry.
Hunter: Reason -- SUPER OP
Warlock: Reason -- SUPER OP

Least Frustrating