So UU is gonna become like the OU M-Salamence era where every team will have to carry a Regirock instead of Porygon2.
GG.
Except with something that resists Fighting instead of being weak to it?
This is actually a point I wanted to touch on. For the most part, Fighting-types in UU are countered, hard, by Crobat, Cresselia, Cofagrigus, Nidoqueen, and rarely by Aromatisse. Both of the new powerful Fighters have a STAB option to break all but one or two of the Pokemon. Terrakion has Stone Edge and Heracross has Megahorn. As you can see, Stone Edge has significantly better coverage on these Pokemon, but Heracross has two (sorta three) things that give him an edge over Terrakion: Knock Off and Guts (+Facade). Heracross can also much more comfortably run an Adamant Nature, giving him more power, even absorbing hits better thanks to a superior defensive typing. Meanwhile, Terrakion can use Rock Polish to oustpeed every single Scarfer viable in UU and down.
TL;DR: Terrakion has mostly usurped Mienshao's spot as the premier "speedy" Fighter an Heracross has completely-and-them-some usurped Machamp's spot as the slower wallbreaking Fighter.
But wait, Lord of Bays! Mienshao has Regenerator, Reckless, and U-turn! Surely he still has a place! And Machamp has Dynamic Punch, Heavy Slam, and Bullet Punch! He's not worthless!
Not really. Terrakion's far better typing (he doesn't get OHKO'd when Crobat looks at him funny, as well as being able to switch in on Cross Poison) and higher speed mean that the only niche Mienshao has is the annoying-but-hilariously-manageable Fake Out Life Orb attacker. Guts Choice Band Heracross is all I really need to say to let you know that Machamp's time in UU is over. If he got Mach Punch, he might have a place, but unSTAB Bullet Punch is not enough.
Seriously, have you SEEN the kind of damage Heracross puts out?