Mark CMG
Creative Mountain Games
...perhaps my confusion lies in the vagueness of "events"?
You do seem to be having trouble with their flexibility, judging by the traditional descripitions you feel they are locked into being used as. For instance, and building off of just your one example but understanding it is in no way limited to this, within the particular campaign a warrior might have an event that requires he defeat (not necessarily kill) his nemesis in actual physical combat while a wizard might need to recover a tome being held by that same nemesis who is threatening to destroy it even as an acolyte's concern is with making sure some prisoners being held by said nemesis, and any number of other concerns. Of course leveling up is not guaranteed since a number of "Events" might need completing before that happens. But, again, if the acolyte. for instance, is building a character based on group unity and preservation, perhaps rather than focusing on releasing the prisoners his Event is tied to making sure all of the party members survive.
And remember, in my own particular system (perhaps you recall reading this elsewhere), completion of an Event allows the player to choose a new Facet (similar to a feature/feat/skill/etc.) for the character that is tied to the Event, in that what the character does informs how that character grows. A character doesn't simply get a pile of predetermined level-up-stuff dumped on them at milestones dictated by XP accumulation.