Throw awat the iLv system, implement a PvE Rank system.

[AdvancedWind]

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Titles for beating content before X do not work as a measure for skill. A player can be perfectly good and not beat certain content due to lack of time, will or even just finding a group to do it. Also, players that started playing the game later cannot get said titles at all, no matter his / her skill. It's a good metric, but not perfect. In fact, there's no perfect way of knowing one's skill other than actually playing with the person. Ilv at the very least allows us to know beforehand if a player's gear meets our requirements; the only true way of checking skill is actually playing together, there's no other way.

With that said, you can check first kill date for most important content by checking the achievement page. If knowing when someone beat X so important to you, just check his achievement page.