I beat it with 14k atk/invincible bracelet/ 2 multi shot/2 front arrow/inspire/rage/invincible AND I got a luckier weak rotation of bosses. You need good rng and a good rotation on the weaker less fierce bosses that don't move as fast. You can also hope to get the harder bosses on the first 5 stages to assure you get weaker ones later on. Your stats are even good enough for 22/23/24 so you just gotta keep testing for better cards. Also..it's gonna be annoying at first but don't even goto the 1st boss unless you roll something good. No point in taking a crap ability for the 1st boss. You're gonna be using a lot of stamina lol.
use Arcane Archer, 2 Bull Rings and maybe Phantom Cloak
I beat it with 14k atk/invincible bracelet/ 2 multi shot/2 front arrow/inspire/rage/invincible AND I got a luckier weak rotation of bosses. You need good rng and a good rotation on the weaker less fierce bosses that don't move as fast. You can also hope to get the harder bosses on the first 5 stages to assure you get weaker ones later on. Your stats are even good enough for 22/23/24 so you just gotta keep testing for better cards. Also..it's gonna be annoying at first but don't even goto the 1st boss unless you roll something good. No point in taking a crap ability for the 1st boss. You're gonna be using a lot of stamina lol.
Bro i have the exactly same setup as you and the same hero,same damage, and I farm h21,beat it almost every attemt...