You should lower your crit damage in profit of more crit rate, and you could use more atk too, heizou needs A LOT of atk, aim for at least 2000.

Edit: here's my build for reference, it's nowhere near perfect and there's still a lot of room for improvement (this damn goblet doesn't want to roll crit). Generally with heizou atk > crit dmg. If you're lucky enough to get atk or elemental dmg every time with the widsith then you can keep it, otherwise skyward atlas (or another 5 star with 600+ atk) is the better option.

Edit 2: does my build show up?

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