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New weaknesses to Steel and Poison while losing it's weakness to Bug and Dark. Weakness to Ghost stays the same.
Now immune to Dragon and 4x resists Fighting and keeps it's resistance to Psychic
Picks up a great type for STAB damage against Dragons, Fighting (Which Psychic did well anyway) and Dark (Which was immune to his previous STAB)
Certainly an improvement to me. Bug and Dark are more common attacking types than Steel and Poison, it resists or is immune to more and he has more options with dealing STAB damage now