I think if you play without auto combat it's actually quiet challenging... until you grinded You Partys Level to a point where noone can touch you... I mean my own Party is around Level 79 with MC leading with Level 81, but I still remember my first encounter with the Brigands at Level 30 or 31 (the first time I actually used Healing Potions in a Battle).
And the Seasonal Bosses are actually Challenging even with my current Level.
Maybe I want to see some Kind of Easter Bunny Boss and stuff... there are still enough Mystical beings connected to festivities around the World Chyos could utilize to challenge his long time Players