The Heroes are ranked based on reliable clears of floor 11 when auto-battling Hunts. Generally speaking, characters who succeed at Auto 11 can also reliably clear the previous stages.
Tier 1: Heroes with excellent innate strength in their kit (element, skills/utility, modifiers) have an edge over those considered Tier 2 Heroes.
Tier 2: Heroes with average kits (element, skills/utility, modifiers) who can be successfully used to auto the hunt.
Tier 3: Heroes with mediocre kits (element, skill/utility, modifiers) are viable, but compared to Tier 2 Heroes, they may suffer drawbacks when used to auto the hunt.