My thoughts on the four Peezy sets:
1) Scarf is not a problem. It's a decent Choice Scarf user, but there are plenty of better ones in the tier. There's really not much to say about this.
2) NP is obviously a stall-destroyer. I've never used NP P-Z, and I've never faced NP P-Z (or if I did it didn't set up so I didn't notice), so I don't really have a lot to say about it. I will say that just about any decently powerful and fast Pokemon with Nasty Plot would be a problem for stall in a tier where Chansey/Blissey don't exist; P-Z just happens to be the only good one we have. I don't think this set is broken.
3) I used Agility a lot last round and have seen it a few times, and it's been disappointing in my experience. The idea is to set up later in the match and sweep through an offensive team, but this rarely actually works. P-Z has no resistances, and this set uses less Speed because of Agility, which together makes it difficult to set up or even bring him in at all because you risk taking a big hit that will put you in KO range for priority later. Several times this has resulted in P-Z just being death fodder at the end of the match because it never got the chance to set up against an offensive team that kept up the pressure. Even if you do get a chance to set up, offensive teams can still work around it. If you're using a Lum Berry, then something like Entei can survive a hit and revenge kill with Flare Blitz. If you're using a Life Orb, then recoil damage quickly puts you in range of priority attacks despite the HP investment. And against defensive teams, this set simply isn't powerful enough. Maybe it's just the teams I've been using that made it difficult for P-Z to set up against me, but I personally haven't been impressed.
4) And then there is Specs. If there's a P-Z set that's broken, this is it imo. Here's what I've been using:
Porygon-Z @ Choice Specs
Trait: Download
EVs: 252 SAtk / 4 SDef / 252 Spd
Timid Nature (+Spd, -Atk)
- Tri Attack
- Dark Pulse
- Trick
- Hidden Power [Ground]
I almost never use the last two moves, so I changed from HP Fighting to HP Ground because I like outspeeding Lilligant and opposing P-Z. I can still hit Rocks and Steels just as hard, and that Speed point is more useful than 2HKOing Munchlax and Ferroseed (who are both rare and easy to handle with other team members).
I opt for Download because, as jrrrr noted, this isn't a tier known for its special walls. It's easy enough to grab a SpA boost, and when you do, nothing is stopping you.
+1 Specs Tri Attack vs 252/252+ Clefable: 59.39 - 70.05%
+1 Specs Tri Attack vs 40/252+ Lanturn: 64.33 - 75.81%
+1 Specs Tri Attack vs 252/252+ Mandibuzz: 53.42 - 63.12%
+1 Specs Dark Pulse vs 252/116+ Slowking: 77.35 - 91.09%
+1 Specs Dark Pulse vs 252/252+ Cresselia: 54.50 - 64.41%
Yeah that's right, you 2HKO max SpD Cresselia. Essentially the only things that aren't 2HKOed by +1 Peezy are Munchlax, Ferroseed, and max SpD Spiritomb (if that even exists). None of them have reliable recovery, all of them are 3HKOed, and all of them are pretty easy to handle with teammates. They also all hate Trick, although it's probably not worth wasting your Specs on them.
And this stuff about P-Z being slow is nonsense. Base 90 is the baseline for RU. Timid Porygon-Z has good Speed, and anything faster than it is "fast". Of those faster Pokemon, let's see which ones can switch in.
+1 Specs Tri Attack vs Sceptile: 122.77 - 144.48%
+1 Specs Tri Attack vs Galvantula: 161.20 - 190.03%
+1 Specs Tri Attack vs Durant: 104.65 - 123.25%
+1 Specs Tri Attack vs Typhlosion: 116.16 - 136.70%
+1 Specs Dark Pulse vs Aerodactyl: 84.43 - 99.66%
Aerodactyl can do it if SR isn't up, but then again, Aerodactyl usually doesn't live past the first third of the match. The rest have no chance of switching in, which means they have to wait for Peezy to get a KO before they can force it out.
But what about priority? Well for one thing, those priority users aren't switching in any easier.
+1 Specs Tri Attack vs Entei: 102.96 - 121.56%
+1 Specs Tri Attack vs Feraligatr: 108.30 - 127.69%
+1 Specs Tri Attack vs Hitmonchan: 111.15 - 130.67%
For another, people seem to underestimate P-Z's defenses. It's not bulky, but it's also not really frail. 85/70/75 isn't terrible. If Peezy is at full HP, not even LO Hitmonchan's Mach Punch can take it down (82.69 - 98.07%), and Honchkrow's Sucker Punch, Entei's ExtremeSpeed, and Feraligatr's Aqua Jet do less than that. Priority is good for beating Life Orb variants, but Specs will survive and KO back, and you better hope you have something else that outspeeds or has priority, or else your team is toast.
Calcs are great and all, but what really matters is how it actually performs, and in this case I can say it's been incredible. Specs Porygon-Z virtually always gets at least one KO, and usually more. With some paralysis support on the few things that outspeed it, it can just tear through a team. It has solid Speed, good enough bulk, and so much power that nothing in the tier can switch in safely. If anything is broken in RU right now, Specs Porygon-Z is it.
