As far as Heracross, it's pretty much an outcast - Terrakion and Conkeldurr pretty much stole all of its thunder.
I'm not sure that it's Terrakion (and I guess Conkeldurr) so much as Gliscor being so high in usage. Heracross' dual STABs are great and it has resistances that Terrakion can't boast, including Ground and Fighting themselves. Terrakion does have access to boosting moves and the speed to back them up, but Heracross can still be a menace if used properly. Overall I'd agree with your assessment, though.
What are people's opinions on water spam? Mono-water is one of the few monotype teams that can be successful, so I'd imagine that sticking 2-3 on a rain team may not be as unviable as it seems. LO Kingdra was 3HKOing Thorn off of base 95 SpA alone, I'm sure that with the proper support (ie a way to remove Gastrodon), a team spamming 2-3 users of boosted Hydro Pump could be frightening to deal with.