To be honest, I'm really torn when it comes to Scraggy. Both Delver and Sir make very good points. When compared to other physical set up sweepers (Dwebble, Tirtouga, Shellder, Axew etc...) it needs less support that every single one. It can pretty much fit on any team and attempt a sweep. As Sir said, if played intelligently it finds getting past its counters quite easy. As Jacob Ninja pointed out, 4x resisting Sucker Punch is a great advantage over other sweepers such as Drilbur who will really fear Murkrow's Sucker Punch.
I'm not sure if the metagame has shifted enough to make Scraggy A rank. Pretty much every team carries Mienfoo but that isn't exactly hard to get past (read Sir's posts). The only real thing it has to fear imo, are faster revenge killers like ScarfKrow which isn't that common.
Looking at Delver's arguments, I think he's right in the fact that Scraggy's predictability lets it down. We all know what it's trying to do. (Although I have been running the moxie-scarf set to some success recently). But then again, isn't Mienfoo predictable? It's almost always running a bulky pivot set with the rare baton pass set and the even more rare scarf.
I'm not saying that Scraggy is either A or S, I just feel that there should be more thought about it as Sir has made a very good case on it being S. All I know is that it is hands down the best physical sweeper in the meta (better than Drilbur imo)*, but that's about all it can do.
*I'm not saying Scraggy is a better pokemon than Drilbur as Drilbur fills more roles such as Wall-Breaker/Rapid Spinner/Revenge Killer. I just feel that Scraggy can set up and sweep better than it.
EDIT: Sorry this is really rambly and I'm not sure I managed to get my thoughts coherently. Tell me if you need clarification.