I haven't actually used Emboar on a team, but I don't think it should be ranked very high. It seems, for a most part, outclassed by other high ranked Pokemon that would be able to do Emboar's job better. For example, Infernape is much faster, has access to multiple boosting moves, and is generally more versatile than Emboar. I could see Machamp being a better CB user because of its ability to absorb status with Guts, and also Knock Off is really good for dealing with things like Gligar. Emboar can't even pull off an effective AV set because its strongest moves all wear down its health or lower its defenses. The best I could see it doing is some sort of Life Orb all-out attacking set, but again, Infernape kind of does this a lot better because of its higher speed and greater versatility. The one thing that Emboar has over these mons is Sucker Punch, but since it's not exactly reliable, it's not even too much of a redeeming factor.
If it were to be ranked, I wouldn't go any higher than C. I see things there that are in situations very similar to Emboar: Exploud is almost entirely outclassed by Porygon-Z (hits almost exactly as hard, faster, Agility and Nasty Plot, Trick) and Mega Audino faces stiff competition from Florges (more versatile with viable CM, immediate recovery in Synthesis, stronger STAB, has Fighting resist, doesn't take up Mega slot). So yeah while Serperior is very very unique and threatening in what it does, Emboar in UU finds itself with heavy competition from things that simply do its job better.
Alright I know this was brought up way earlier but I wanted to see some discussion on Pangoro. Simply put, stall has NOTHING to kill this unless they want to run something like Crobat (and even then, have fun switching in if it's not SD). With SD Lum, Pangoro finds many opportunities to set up against defensive teams. If it runs Iron Head, it OHKOs every Fairy except for Granbull, which can be OHKOd if Pangoro runs Gunk Shot instead. I'm fairly sure that the only other ways that stall can deal with SD Lum Pangoro, besides unorthodox things like Crobat or Whimsicott, is by haxing it with two Scald burns in a row or dodging a Gunk Shot. Its ability to keep itself healthy with Iron Fist-boosted Drain Punch is amazing for it. CB is also very good because it 2HKOs like everything except for physically defensive Gligar. The speed loss from Hammar Arm is an issue though, as it makes it more susceptible to Scald and other attacks. Pangoro's in C right now but I think it should go up to B- at least.
Edit: forgot to say that Pangoro's bad speed and /eh/ bulk makes it not great against offense, which is one of the biggest reasons it's held back from a higher rank.
