You should be focusing more on dodge/block as survival and getting out of the way of enemies in general. Also CCs such as stun or Frozen to encase enemies in ice or slow them down completely for survival and DMG dealing. Hence why Frozen is so good.
Yeah HP doesn't matter at high floors since the enemies can one hit you anyways and even if not, the thorns will hurt unless you rapidly Regen by HP on Hit or HP Regen.
High damage that can kill them fast or crushing blow (with crushing flames if fire attacks) also speeds up clearing floors and sometimes survival.
Flintlock especially since you can shoot from Afar . Stealth skill to dodge all attacks for 1-3 seconds (more second by hero points) and sometimes smoke bombs to dodge a fatal attack and a rapid amount can make you almost invulnerable unless you miss timing.