Since this is the only analysis for regular Heracross that's currently up, we're holding off on deleting it until its UU analysis is finished so that people interested in using it still have an idea as to what sets it can run.
i'm not seeing the correlation between best sets and usage.. and determining how much "stall" there is like isn't affected by ladder quality, stats will tell you how much a mon is used on ladder but usage =/= viability
The best explanation I can figure is that we aren't low enough to attract the people that want to use their favorites is a tier they work in and that our mon distribution tends towards the sort of oddball stuff that not all fans of the games are into. Stuff like salazle, registeel, or comfee. We do have a few fan favorites, Zoro, umbreon, and venusaur come to mind. But the majority of our mons tend to fall more towards "wtf?" than do towards "Super cool". So I think we loose out a lot on scrubs who are in it because they like Pokemon. Just taking a stab at it though. To be honest the question has perplexed me at times as well.
Tldr: too much gen 5-7 not enough 1-3 (not that I'm complaining)
The 84 EVs allow you to outspeed uninvested 50 based mons (Diancie, Donphan and Regi), while being faster than Regi is indeed relevant, it's more recommended to just use Max Speed (Adamant) on Dhelmise then you outspeed things like Umbreon and Mantine as well
Outclassed by Florges as a fairy. Normal/Fairy isn't very good in this meta. The Fighting resistance is important and the only Ghost hits it super-effectively with Iron Head anyways. It's also extremely passive, relying on Wish + Protect for recovery gets it worn down easily. Lacking Leftovers also hurts.
In addition to what was said above, if you're opting for a Calm Mind set, Comfey generally does it better. It basically only outclasses it by having access to some moves like Fire Blast but is far slower w/ no Priority so it can't exactly sweep.
Well, their Z-Move power is the same. So without running any calcs, you wouldn't be able to OHKO Bulletproof Kommo-o w/o popping your Z-Move, and you would be forced to go for a Fire Blast (miss chance) vs Chesnaught. Lower chance to OHKO Venusaur and Mantine at +2, also from the top of my head. Probably more, Salazzle is an offensive mon so the increased chance of poison isn't really relevant too often.
The viability rankings are for discussion :D, so in the future a justification or a post aguing for a heliolisk rise would actually be super great to stimulate some discussion on the forum.
Basically it is just fast enough where a lot of offensive pokemon outspeed it, and just not strong enough where it struggles to break defensive Pokemon. This kinda pigeonholes it into being a specs user (scarf is bad because you lack the power without a booosting item to actually revenge kill stuff) but even at that role it isnt as scary to switch into as something like Yanmega or Kommo-o. Electric/Normal isnt a grrat typing offensively or defensively, and it doesnt have a great movepool outside of STABs. The only merit it has is breaking through the old Mantine/Rhyoerior defensive core but even just by throwing a grass type into the mix Heliolisk's job becomes even harder.