Metagross @ Choice Scarf Trait: Clear Body EVs: 12 HP / 244 Atk / 252 Spd Jolly Nature (+Spd, -SAtk) - Stealth Rock - Meteor Mash - Explosion - Trick Salamence (M) @ Life Orb Trait: Intimidate EVs: 80 HP / 176 Spd / 252 SAtk Rash Nature (+SAtk, -SDef) - Roost - Brick Break - Fire Blast - Draco Meteor Rotom-W @ Leftovers Trait: Levitate EVs: 252 HP / 164 Def / 88 Spd / 4 SAtk Bold Nature (+Def, -Atk) - Will-O-Wisp - Hydro Pump - Thunderbolt - Shadow Ball mein teil (Tentacruel) (M) @ Leftovers Trait: Clear Body EVs: 204 HP / 88 Def / 40 Spd / 84 SAtk / 92 SDef Calm Nature (+SDef, -Atk) - Surf - Rapid Spin - Toxic Spikes - Hidden Power [Electric] Jirachi @ Light Clay Trait: Serene Grace EVs: 252 HP / 108 Def / 148 SDef Careful Nature (+SDef, -SAtk) - Wish - Reflect - U-turn - Light Screen Breloom (M) @ Toxic Orb Trait: Poison Heal EVs: 48 HP / 252 Atk / 208 Spd Adamant Nature (+Atk, -SAtk) - Substitute - Focus Punch - Spore - Seed Bomb will add descriptions and stuff later rotom-h is a threat and so is dd mence but other than that everything iz nas
You've already said it, but Rotom-H is going to give you some trouble. Powerful scarfers can also give you a hard time. Heatran ( especially of the Torment variety ), could become a problem once they get a sub up. On the same note, one Rotom is out of the picture, Gyarados can come to play. Something to setup as revenge of Gengar could be helpful. Your Salamence seems to be mixed, so a partner like Magneton or Magnezone would always make its life easier. Jirachi seems to be filling the role of wish-passing to it already, though. SD Lucario should be something to take into account as a threat, since it could find various openings to setup. Salamence seems to be the only buffer against it - and it has life orb.
I'll just address problems with each Pokemon individually. I'm no expert on synergy. That Metagross is going to be 2HKO'd by most common anti-leads, even after Trick, including Dragonite and Starmie. Your Stealth Rocks have no chance of getting up, let alone staying intact. Salamence shouldn't even bother with that Brick Break, it's not going to be strong enough to break even some of NU's walls. With that EV spread, the only physical attacks that will even have a prayer of doing damage are Earthquake and Outrage. This is especially notable because you're letting Blissey wall you and Thick Fat Snorlax set up on you, and Breloom's the only thing preventing them from walling/wrecking your team. Rotom seems okay. I'd give up one of its moves for some kind of recovery, as if Jirachi is killed it has none. But that's not entirely necessary. Tentacruel is okay but I highly doubt that HP Electric will do much against most Water-types anyway. Suicune will still set up on you and Vaporeon will still wall you (though in that case, it's mutual.) I'd give it up for a stronger move, like Ice Beam or something? Can't complain about Jirachi and Breloom. The sets are fine for what they have to do, but I feel you're relying too heavily on Breloom here. (I hate Jirachi and Breloom with a passion anyway, but that's irrelevant.)
About metagross, actually scarfed like it is, it will get its rock up except against aerodactyl which could taunt it -- then metagross might as well meteor mash to destroy the opposing lead, then come back later for rocks. In short the only time it couldn't get rocks up would be against aerodactyl. You're saying it's 2HKOed by anti leads, but suicide leads are 2HKOed anyway. So it acts like a suicide lead (against antileads only, and still setting rocks) and then can come back later to do some damage with meteor mash/... I think it does pretty good for a lead.
I had assumed he wasn't JUST getting Rocks up, but also trying to hurt the opponent. In which case really I've always felt scarfing a lead just to get to beat Azelf to SR is stupid anyway, they can always be set up later and they aren't ridiculously important enough to lock the lead into just to ensure they're up from Turn 1. But hey, if that's your thing, feel free to keep using your Metagross like a weird flinchless version of Scarfrachi lead.