MMORPG.com: It appears that you are reset from level 120 back to level 60, what was the rationale behind this?

Joon Kim: To clarify, it is only Mastery that reduces one's level back to 60, Heroism does not. As to why we did this? There are several reasons as to why, but one of the most significant reasons was to preserve the party system for Masters and Heroes. Benefits of the party system include group buffs and a bonus to EXP; aspects critical for leveling and battles. If a Master or Hero started maintained their 120 status, they would progressively find themselves with less and less leveling partners, thus denying them a substantial aspect of the game.