(assuming +2)
-Skarm is 2HKO'd by Stone Edge after Rocks
-Latias is OHKO's 63% of the time by Stone Edge
-252 HP Gliscor is 2HKO'd by Stone Edge (Way more HP than AcroBat)
-Tornadus is 2HKO'd by Mach Punch after SR
-252 S.Atk Modest Rotom-W can't OHKO Breloom with HP Fire, while 128 HP is eaily 2HKO'd by Mach Punch
-EBelt HP Ice Landorus can't OHKO with HP Ice
-If Poli/Slowbro are a problem use Seed Bomb, it's in AC
-Reuniclus/Gengar aren't meant to be dealt with by this set. Your reasoning is basically "Why can't you deal with Pokemon that counter this set?". It's kinda like saying why can't Bulk Up Breloom counter Celebi. Everything needs team support. I mean, why should anyone use Starmie when it's countered by Ferrothorn? Everyone run HP Fire on Starmie! Thing is, there are alot of ways to deal with what stops this set. Scizor is awesome for trapping those Psychics and using dual priority. This set kills 6 out of the top 10 Pokemon though, so shouldn't it see some use even if it has counters?
@Ojama, The combination of Mach Punch and Stone Edge is insanely powerful. You'll almost always get to set up because of Spore, and Life orb only bolsters your attack. If you feel like you want a powerful move, run something over Spore. You aren't limited to these four moves, just look at the AC section.
EDIT: forgot to mention the end of alexwolf's post. Just look at the analysis. There's no way Toxic Orb can be main. You lose so much power and so many KO's by running Toxic Orb. It's a good option, just not a good primary option.
I don't really get why you post these calcs... All these are 2hkoes at +2. How are you going to get 2 hits?
- Skarmory will lose 50% of it's health and ohko you.
- 252 Gliscor can simply Toxic Stall you if it is the max HP variant or kill you if it is the AcroBat one.
- Modest Rotom-W deals 83.52%-98.85% with HP Fire, so after SR and the LO recoil you will suffer from using Mach Punch you are always OHKOed.
- E-Belt Landorus deals 79%-93.5% with HP Ice, so after LO recoil and SR you have around 50% to be ohkoed. Factor in Sand damage (we are talking about Landorus right?) and the odds are not in your favor.
- Tornadus just takes one Mach Punch and then OHKOes.
- If you use Seed Bomb then a host of dangerous set-up sweepers, such as Dnite, Mence, Lati@s, Volcarona, Venusaur and more, use you as set-up fodder. Grass + Fighting is god awful coverage if they are your only moves.
My problem is that this set is inferior to the other on-site sets, while it can't get past most of Brelloom's usual counters. Why use this set and lose the bulk provided by the Bulk Up variant, if i am going to get walled and forced out by the same pokes anyway? You are using SD on a frail slow poke, and your only priority is a 40 BP attack, while your coverage is limited no way how you see it. Just stop a moment and think how many viable SD users we have in OU? We had Garchomp, Scizor, Lucario and maybe Infernape.
Lucario and Scizor are viable SDers because they have powerful priority that can actually kill things, not almost kill as Katakiri showcased, while also having a superb defensive typing letting them set-up easy, and finally have exceptional coverage (Lucario). Breloom can find many set-up opportunities due to Spore but then his coverage is very limited and his priority is still weak.
Garchomp had bulk, power and speed, while Breloom has only power.
And Infernape which is the least viable SDer, and is rarely seen, has power and speed, while also having priority, so once it sets up, if you have eliminated faster mons, he has a chance to sweep.
But how can Breloom do this when he is outsped by every offensive mon, doesn't have strong priority, and doesn't have the bulk to take hits from revenge killers?
As i said again, i am not saying that this set is useless, it certainly have its uses, i just don't think that these uses are enough to justify a main set.