well, since you mentioned the viability rankings, i'm guessing heracross is c+ because of team slot competition. i think your post would be more persuasive if you focused on this more instead of how hard heracross hits.
a lot of pokemon hit hard. but you also have to build a team around them. heracross's defensive utility is spotty. offensive teams (and even a few balances) rely on fighting-types to check bisharp, but heracross can't switch into iron head and has to be at full health to survive +2 sucker punch. defensively, a pokemon just offers more utility, switching into the ever-annoying heatran as well as tyranitar (also beating the rare dd megatar) and offering more speed (making it more than total fodder for slow-ish breakers like garde, zard y, landorus, and manaphy). not that heracross doesn't have niches of its own (mostly the ground resist), but eh.
just an opinion, but i like pokemon that afford you flexibility in both team building and in battle and don't require very precise execution to work well. a band set is hard to switch into on the first turn but then is forfeiting free turns, and toxic orb is wearing itself out such that even opponents who are very weak to it can limit its impact (ie "play around it").
i'm assuming you have more experience with heracross than i do. do you have some sample cores or preferably a team or two that display heracross's effectiveness within a team strategy?