I have been really busy these days, and since this still hasn't received proper rate, I thought I'd give it a shot :D
Ok, this team pretty much covers the majority of offensive threats except for a few of them. Those being Heatran, Gyarados and Infernape. Heatran OHKOes / 2HKOes your whole team without much retaliation. A Choice Scarf Heatran outspeeds your whole team and KOes 5/6 everything in sight using Fire Blast. Both Gyarados and Salamence cannot switch-in reliably as both of them is outsped and 2HKOed after taking SR damage. Earthpower takes care of your own Heatran who cannot risk a tie. While Adamant Gyarados can be checked by Jolteon since it can revenge kill it even if it gets a DD, it is your late game sweeper and the Pokemon you based your team around it, and you don't want it to be checking things. If you manage to encounter a Jolly Gyarados, it will 6-0 your team. It can set-up on Scizor locked onto Bullet Punch, Pursuit and Superpower or Heatran locked onto Earthpower or HP Ice. From there it is just pure domination. Infernape, mainly MixApe versions seem to be a bit problematic as nothing can safely switch-into any of it's attacks without risking the KO. You could revenge kill it with Heatran and Jolteon but Infernape is just guaranteed a kill per match against your team. Bulky DD Salamence can also be a pain for this team to deal with, since it cannot be revenged by Scizor and uses him as a set-up fodder.
Now, in order to remedy these issues, the best change you could do is replace Gyarados with an offensive CM Suicune. Suicune will be extremely benfeficial to this team as it can keep the threats mentioned above. Gyarados wasn't bringing much to the table as I see it since the threats it handles such as Lucario is already covered by ScarfTran and Suicune can still check it, and your Salamence with it's old MixMence set can easily break through stall as it was designed for. Suicune still beats Ground types your Gyarados to beat, and provides an effective Salamence, Heatran, Gyarados and MixApe counter. So, that change won't be such a big one actually, it will improve your team's ability to deal with threats. In addition, Suicune pairs nicely with Jolteon, since they share some common counters. Here's the Suicune set:
Suicune @ Leftovers | Pressure
Timid | 252 HP / 40 Def / 216 Spe
Calm Mind | Surf | HP Electric | Ice Beam
The 216 Speed EVs allow you to outspeed max speed Adamant Lucario and max speed Timid Heatran.
I don't like the fact this team has three Choiced Pokemons at all. You will be obliged to switch-out a lot and take residual damage and give much more opportunities for threats to set-up. Since you are basing this team around Jolteon, I would like to suggest an alternative set that I have found to be very effective on Jolteon. It is the Charge Beam + LO set. Late game, you can switch him in so he can clean the rest of the opponent's team, except you can switch between attacks which will grant you much more versatility. This set is much more dangerous since if you use Charge Beam once and get the boost you will have the same power as the Specs set except you have the ability to switch between attacks. I would at least give this set a test and see how it goes.
Jolteon @ Life Orb | Volt Absorb
Timid | 4 HP / 252 SpAtk / 252 Spe
Thunderbolt | Charge Beam | Shadow Ball | HP Ice / HP Grass
This is a very solid team btw. Good Luck!