NP, I don't think there is much doubt about the effectiveness of the set. Clearly, none of these "counters" are typical in the current metagame. I mean really... low/no speed Breloom and Focus Punch Weavile are not exactly popular choices at the moment.
Closer to the current metagame are the Metagross set (anything on a metagross is more or less scary) and possibly the Toxicroak set. No one uses toxicroak... but if someone did they would probably use the standard rain dance set.
As you stated the best part about this set are that the counters are not in the current metagame. Yes, obviously, there are counters to this set as there are with every set. However they would almost have the soul purpose of countering Wallrein (if that's what you are calling it)....which seems unlikely. Metagross is the exception but even then it is unlikely that the majority of teams don't have a metagross to counter this.
Toxicroak counters it but who uses a toxicroak? maybe to counter Heracross, as it resists all of its normal attacks (megahorn (4X resist) Close Combat, Stone Edge, Pursuit)....but even then it is likely 2 HKOed by Choice Banded CC from Hera
Closer to the current metagame are the Metagross set (anything on a metagross is more or less scary) and possibly the Toxicroak set. No one uses toxicroak... but if someone did they would probably use the standard rain dance set.
As you stated the best part about this set are that the counters are not in the current metagame. Yes, obviously, there are counters to this set as there are with every set. However they would almost have the soul purpose of countering Wallrein (if that's what you are calling it)....which seems unlikely. Metagross is the exception but even then it is unlikely that the majority of teams don't have a metagross to counter this.
Toxicroak counters it but who uses a toxicroak? maybe to counter Heracross, as it resists all of its normal attacks (megahorn (4X resist) Close Combat, Stone Edge, Pursuit)....but even then it is likely 2 HKOed by Choice Banded CC from Hera