You make several decent points. I think you took things more literally than I meant (I was just making a point that stall always uses revenge killers, not actually trying to compare each individual mon used to do it) but actually I see what you're saying.I don't claim to know anything about UU, so I won't comment there. Though for what it's worth, there is the fact that Mega Aero is much more threatening than a SDef Espeon will ever be.
I will say, however, that Dugtrio actually, y'know, traps the things that annoy stall for a guaranteed KO as opposed to forcing it out, doing some damage to one mon then potentially getting trapped itself. Not to mention in order to bring Espeon in to RK, something would have to be KO'd in the first place due to most Stall mons not using U-turn/Volt Switch and BP being banned. That is not the case on OU stall, so comparing Espeon on Dugtrio is not fair to your argument.
Finally, forcing a playstyle to adapt to using a subpar moveset just in order to check one threat is usually a good sign that that threat is unhealthy and likely merits a suspect - the concept of overcentralization. Just because it's been done before doesn't make that any less true.
Edit: Actually, you kinda proved my point right. UU Stall including Mega Aero means that it actually has a switchin to Toge, and as such doesn't have to sacrifice a mon to threat it out offensively. However, RU stall is essentially forced to sac a mon then attempt to revenge Hera, on which it can simply switch and return later whether by pivoting, double switches, or after having a mon be KO'd on its side.
However, I'm still in disagreement over acro. To me at least, thats not so much running a subpar move to cover one overbearing threat than it is naturally having a countermeasure to a particular pokemon that threatens that play style. It's not a result of overcentralization, it's just players responding to a threat, which is how team building should work. I feel like this debate is starting to repeat itself, though, and thats probably annoying to everyone else in the thread, so I'm probably done talking about heracross for the time being