It’s obvious that some Heroes are better than others, but it also highly depends on color, synergies with other heroes, and the enemies or situation in hand.
I think usefulness is a key criterion: some heroes are good in various situations - others are niche.
Therefore I think it may be useful (even if not entirely precise) to gather heroes into a hierarchy “these heroes are generally more useful than those heroes”.
I think this classification can be a useful guideline when selecting which hero to level. Clearly an important decision with the rarity of 4* and even 3* unfarmable ascension materials.
I’ll be happy to get your feedback if this classification makes sense (I’m quite certain now everyone will agree - so it worth also explaining why you think some classification is wrong)
(Routinely being edited based on feedback)