Hello, Heigan has never been easier:
Mulligan for Gargoyle and SW:D or SW:P for his initial creature (if he can he will coin + Demonfire)
Then aim for a gargoyle on the leftmost side and is already almost GG. If you don't have gargoyle, eggs will buy a lot of time aswell. Then play control and buff your minions. Go for big healthpools and favorable trades, oneshotted him with this list.
Good luck everyone!
EDIT: Added Inner Fire, thank you for feedbacks!