Unlike many modern fantasy-based MMOs where choosing one's class is largely independent from the selection of one's race, each of the six player races in WAR have three or four of their own, unique classes. While every class (or "career") in the game falls into one of four archetypes - Tank, Healer/Support, Melee DPS and Ranged DPS - they all have their own individual career mechanics.
For instance, every time a Dark Elf Sorcerer casts a damage-dealing spell, they will accrue "Dark Magic" points. The higher their Dark Magic pool, the higher the chance of scoring a devastating critical blow - but they also have an increased likelihood of causing a Backlash when they cast, taking not-insignificant damage. While each career's special mechanics are unique within their Realm - a Dark Elf Sorcerer, Greenskin Squig Herder, and Chaos Magus all play very differently despite all being of the Ranged DPS archetype - every career has a "mirror" in the opposite faction. The counterpart to the Sorcerer is the Bright Wizard of the Empire, the Blade Dance of the High Elf Swordmaster is set against the Brawl of the Black Orc, and so on.
Even though every career has its own flavor, they all share the same core resource: where other games have Power, Mana, and so on, every class in WAR uses Action Points (or AP) to activate abilities. AP constantly regenerates over time while in combat, much like the Energy system used by the Rogue class in World of Warcraft. Both AP and a character's health refill extremely quickly while not in combat, so there's no need to sit and rest in between fights - WAR has very little downtime, which is nice.
However, while there may not be much downtime between fights, combat itself feels rather slow, particularly with melee classes like the Swordmaster. A more apt term might be "sticky," really - there seems to be a slight disconnect between when the game's display tells you that an ability is available and when it actually is. It's very slight and hardly makes the game unplayable, but the delay makes for combat that just feels slightly clunky. It's possible that this might have just been the result of lag, but the consistency with which it keeps occurring (and the lack of any noticeable lag in other aspects of the game) makes me doubtful.
Players who select caster classes will encounter another problem - though being attacked while winding up a spell will slightly push the cast bar back, the animation continues as normal. It is not uncommon to see my Sorceress fling her spell at a foe and have it connect ... only to have her stand around apparently doing nothing until the spell actually finished casting and dealt damage.