I did post this previously, but I didn't put so much detail into what the pokemon did and it got locked. Lesson learnt.
Team Building:
First of all. I wanted to base my team around Heracross.
I started out with a Close Combat/Megahorn/Stone Edge/Earthquake set, using a choice scarf.
The EVs are obviously pretty standard, max attack and speed.

I figured that Heracross' biggest bane is flying type moves, coming from the likes of Torn and Torn-T, so I wanted something that could pass 375 speed. The only real option was Jolteon. I chose a Timid nature in order to outspeed max speed Torn-T, and since the aim was to outspeed Torn-T, which is rarely scarfed, I figured a choice scarf would be wasted. The obvious choice was to spec or LO the Jolteon, but I thought that an Expert Belt would boost the power of his attacks, and allow me to feign a spec set.

Realising some potential, I settled upon HP Fire, in order to knock out Ferrothorn coming in to take the T-Bolt. Finally, I chose Magnet Rise to troll anything attempting to EQ or EarthPower me.

Since Jolteon was ground-weak, even with magnet rise, I wanted something that could take out ground types with ease. I toyed with Keldeo, as it's speed and power are pretty immense but figured that others might do the job better. I looked at Rotom-W, but actually went for Rotom-M, as it has immunity to the ground type STAB, and resistance to quakeedge. The weakness to Ice is a drag, though.

Now, I wanted a spinner and also something that count take Ice attacks. Forretress seemed the way to go.Stealth Rock and Rapid Spin are obvious. I wanted something that could heal me though. I ended up going for protect and toxic. I chose a calm nature, and 216 Sp. D EVs to hopefully shrug off the occasional HP Fire that catches me offguard.

With 3 offensive pokemon and one defensive, I wanted another defensive to compliment Forretress. Also, I was worried about Forretress' lack of recovery. As a long-term Porygon fan, I brought out the P2.With Recover, BoltBeam, Trace, and Toxic, plus the Eviolite's defensive boost, P2 is a great mixed wall. This, particular P2 was oriented towards physical defence, despite already having Foretress there as Showdown's default is the special defence, so I figured it would catch a few offguard.

Finally, I needed a special wall. The obvious choices of Blissey and Chansey sharing type-redundancy with P2, I looked through and found I had a serious weakness to fire. I went for an offensive Heatran instead, as again, lack of recovery seemed worrying.

Still weak to fire! Urgh. I swapped Rotom-M for Rotom-W. Finally, I needed something with Rock Slide or Stone Edge to counter Volcarona. Out went Forretress, and in came Donphan. Still fullfilling the role of the spinner, and with Ice type attacks deflectable to Heatran, I went for a slightly more offensive donphan than the norm, leaving P2 as my only dedicated stall. Great physical bulk, strong attack meant that Rock Slide was as good of a bet as any. It 1 battle, though, before I realised just how easily Volcarona could rip through Donphan. Not the best counter when you get OHKO'd. My final choice? Snorlax. Great special bulk, decent attack and that ever-so-handy element of surprise. Of course, it cannot spin, but none of my team is weak to Stealth Rocks, so I thought I might be able to get away with it. Stealth Rocks were swapped for Return, as Heatran has SR anyway. I stuck Brick Break on to deal with Ttar.

I soon changed Snorlax to Tyranitar, due to how generally unhelpful Snorlax was outside of Volcarona, but Ttar gets nailed by a super effective bug-buzz. Gyarados ended up being the best choice I could find.

Regarding missing EVs: Many of the spreads on the images only add to 504 - the other one I thought to be to insignificant to include, but is generally put into speed to outspeed other versions, or is included for additional bulk... 1 extra hp FTW!

Ahh... Heracross. The king of UU. A great pokemon, with amazing dual STABS, viable in Ubers and yet? It still remains sleeping down in UU. I wanted to really test run it in OU and build my team around it.

Chosen for no other real reason than because I like Heracross, and as a scare to the pink blobs, I set him up as my late-game sweeper and revenge killer. The choice of a choice scarf is pretty obvious for those roles, and particularly patches up Heracross' disappointing speed stat. Quakedge and Bug/Fighting STABS give him some pretty great coverage, though Close Combat is generally the main move he'll use unless I'm predicting Jirachi to come in and ruin the fun.

Now, Heracross' glaring weakness to flying - particularly Tornadus shone through many other things after that. I wanted something that could out-speed Tornadus, without having to be scarfed. My choice? Jolteon.

With speed stats optimized to juuust outspeed Tornadus-T (376 speed, compared to Torn-T's 375), he avoids the speed tie and can hit with super effective thunderbolts. Whilst Torn-T is most commonly used in the rain, I didn't want to risk Thunder in the sun or clear skies.

Slightly stranger is my choice of hidden power though, which leaves him walled by threats it could normally beat such as Gliscor. It was put there to counter Ferrothorn, who is a common switch in to take the Tbolt. The expert belt is there to ensure I can still do that if I mispredict. Finally, Magnet Rise abuses the lack of specs and allows Jolteon to escape from Dugtrio, and troll other Earthquake users.

So, whilst I had a great pair of offense, rounding out the team is Porygon2.

A pretty standard defensive duck, it trades power for defensive prowess. In testing on PO, I managed to switch it in on a Shedinja and trace wonder guard, which sold the ability to me immediately. I went for Boltbeam instead of Tri Attack/Shadow Ball or Tri Attack/Thunder Wave because it's nice to occasionally catch a Dragonite or Gyarados off-guard, and put a stop to them setting up on my defensive duck. Volcarona is still a major issue though.

Originally I had Snorlax, but I swapped it for Gyarados.

Both were designed to counter Volcarona and so both had rock slide, trading some power for accuracy. Both worked, but Gyarados was by far the better for enemy rain teams and those which do not have Volcarona on it.

Dragon Dance, Rock Slide, Earthquake, Waterfall. Is there really much to say? It's your standard set-up sweeper with max speed and attack. I'm really horrible at coming up with efficient EVs, and I figured that that would do. It's pretty much there for if Heracross has died in the course of battle from missing a Stone Edge or something, as well as countering Volcarona. Yay for Stone Miss!

The pink blobs were still a major threat though, because what kind of stupid player leaves Blissey in against Heracross? Along came Rotom-W.

The standard trick set is designed to shut down walls, Ferrothorn, and other annoyances. Whilst being able to run a decent scarf set itself. Whilst I am loathe to use Hydro Pump due to it's accuracy, it presents itself as the only option, HP Water aside. It shares good offensive synergy with Heracross and even counters some Jolteon switch-ins with Hydro Pump and Levitate. Whilst the type redundancy with Jolteon and Gyarados for electric and water respectively kind of blows, leaving this team with a small electric weakness.

Finally, I wanted something to cover a fire type weakness I had at one point of making this team which has since disappeared, but the pokemon remained!

Whilst really quite overused, this bulky offensive Heatran is my only Stealth Rocker and my only counter to Genesect should Jolteon go down. Dragon Pulse gets the drop on Dragonite that may switch in to take a Lava Plume. Lava Plume itself was chosen for the burn chance and accuracy, whereas Earth Power is included for additional coverage. It originally was needed to bring the team together, however the others synergise much better now so I could change Heatran if I could find something better to use.

Changes to be tested:
Rotom-Mow over Rotom-Wash
Scarf set for Heatran
Pretty Interesting team you've got here.
Im not the best person for this but your team does carry a really big weakness to pretty much any Virizion set and even though it isnt seen much in OU it could be a big problem for your team so you may wanna try out Choice Scarf Heatran so you can outspeed Virizion and take it down before it causes some serious damage to your team
I can't say I saw Virizion at all during testing. Choice Scarf Heatran sounds like an interesting idea, though Virizion would already be outsped by Jolteon, who could then HP Fire or Volt Switch into Heatran. Virizion isn't going to stay in against Heatran anyway unless it's being used for fodder, in which case outspeeding doesn't seem all that important.
Have you considered Rotom mow in place of rotom wash? It's patches the electric weakness and the team would appreciate something that can hurt gastrodon and it's fellow water ground brothers outside of toxic stalling thanks to porygon2. Granted fire would be more of a present weakness than the electric but you got porygon2 and heatran and even gyrados to take them anyway.

I would suggest the specs set. I see you don't mind double scarfs but it bugs me. Since you don't mind that, scarf would work just as fine.

Cool team. First off, your Jolteon set needs some patching up. Why would you run Magnet Rise on Jolteon only to evade Dugtrio, when you can just use Hidden Power [ICE] > Magnet Rise and kill off Dugtrio straight away? Considering Duggy also threatens your Heatran a lot, this is very beneficial in order to get him out of the way. Considering that you have Heatran and Heracross, both of which beat the crap out of Ferrothorn, I didn't think that having a HP [FIRE] E Belt lure set was the best set anyway, and currently your set is massive set up bait for dragons like Dragonite ,salamence and Haxorus, as well as being an invitation for Latios to come in. Considering you can't have 2 hidden powers, use Shadow Ball > HP [FIRE], as with Jolteons barren movepool it has no better options, and it hits Latios and Ghost types for slightly higher damage than your current options. I also reccomend Life Orb > Expert Belt for a guranteed boost to your moves, and the boost is very much needed to give Jolteons weak attacks a bit more kick to them.

Your team also has it rough with defensive Gastrodon, as it walls all your offensive pokemon, as Heracross can't take burns, and your only answer is Porygon-2, who will find itself crippled in the process by Gastrodon's own toxic. To remedy this, simply use HP [GRASS] > Discharge on Rotom-W. Discharge is a luxury on Rotom-W your team simply can't afford, the extra 10% power and non switching abilty it has over Volt Switch being much less beneficial than the abilty to beat something which at the moment, damages your team a lot.

On Gyarados definitely use Stone Edge > Rock Slide. Stone edge has far greater power than Rock Slide, and 25 more power is definitely worth giving up 10 accuracy for any day on Gyarados, as it that extra power is always nice to have behind your attacks. Also on Heatran use Hidden Power [ICE] > Dragon Pulse. Using Un-STAB Dragon moves isn't really ideal on any pokemon, and Ice really compliments your earth power well, hitting Landorus, Gliscor and the dragons that Dragon Pulse was hitting for high damage

GL with the team
Right. I tried out some changes.

Firstly, HP Grass seemed to work better than using Rotom-Mow, however, I didn't really like the loss of discharge. The set I ultimately wound up with on Rotom-W was:
-HP Grass
-Volt Switch
-Hydro Pump
Whilst the loss of trick kind of sucks, I had more success with this set.

Secondly, I run Stone Edge on Gyarados and it screwed me over more times than I care to mention. Apparently, it can't learn it but I swear it had it before? Weird. Perhaps I just got it confused with Snorlax...

Third, Jolteon swapped from HP Fire to HP Ice, though I kept the Magnet Rise/E-Belt set. It may be slightly gimmicky, but I like it.

Lastly, Heatran got HP Ice. Landorus, and Gliscor outspeed and OHKO, so it doesn't really help there, but it does hit harder against the dragons as they are predominantly dragon/flying.