We get this question a lot so I'm doing my part to get the word out:
Even though it's an MMO, Eternal Crusade plays out like a proper third-person shooter and in this regard one of our big inspirations is Space Marine. You point where you want to shoot or strike and hitting your target is largely based on skill. There are no ability bars or auto-attack systems.
Of course, we also have an RPG system, so for example the spread on your shots will be based on a variety of factors, including what kind of gun you're using, its upgrades, and an accuracy score from your character. Games like Deus Ex work this way.
However, since this is a PvP-focused (though not exclusive) MMO, your progression is largely horizontal, meaning that you unlock new things to equip on your character, but they'll generally have to replace other options and choose how to specialize. Think of the recent equip systems in Call of Duty, War of the Roses, or various mech games as examples here.
Each faction has ~5 primary classes, and depending on how you build your loadout (accessories, weapons, items, etc) for that class there are a multitude of possible specializations. Eternal Crusade is also a massive tactical wargame so not every specialization will be equal when going toe to toe with each other - you should either bring friends to make up for your weaknesses or deploy your loadout in the circumstances that favor your specialty. Since you can change classes and loadouts whenever you deploy to the field, you're not locked into your choice for hundreds of hours or anything.