I've been playing this game for a LOOOONG time. Long enough that I remember the debate over combo back when someone first figured out they could cancel the animation and use another attack.
So lets think about this for a minute.
In most MMORPG's the mages rule the place. Nobody else has a chance against a high level mage with good items, they'll simply flatten you like a steam roller. A melee type can't even get to them to cancel their attacks.
Combo evens up the playing field tremendously in KO. IMHO, combo gives melees an advantage under lvl 60, and keeps things pretty even above those levels.
But combo was called cheating and hacking when I started playing. This debate over combo went on for MONTHS, and the GM's finally ruled that it was legal, since it didn't affect cool down times but only how fast a rogue or warrior could discharge all skills. Besides, there was no real way to catch anyone using combo.
Combo is a SKILL you have to LEARN, it isn't given to you as a gift by the server gods. This makes for a different level of skills even when characters are otherwise identical. People PRACTICE combo, you must practice to get good at it. (I'm fairly good at it myself.)
I believe combo is what made the PVP system in KO what it is (was? ). And combo was NOT intended by the programmers of the original game, it was an accident.
The best PVP system I've ever played, and it was a complete accident. What a laugh.