Hi there! This seems like a pretty decent team, but I would like to give you a few suggestions.
First off, Weavile. It really doesn't benefit from leftovers all that much since it can't take that much of a beating. I would personally use a Choice band set (which I have used myself with great results) I say this only because you have Espeon to deal with hazards so taunt isn't needed that much. Ice Shard / Night Slash (or Pursuit) / Low Kick / Ice Punch should be a good set with a Jolly nature.
Next is Manectric. As perviously stated, it's kind of in Thundurus' shadow for the most part. I can see you are really attached to using him, so you should use something that Manectric can do and Thundurus cannot, and that is tricking a Choice item on to potential walls. You see, Thundurus is walled by S.Defensive Gastrodon and even Quagsire to a lesser extent if it is carrying Focus Blast / Hammer Arm. If it has grass knot, it's walled by Chansey and back. Manectric can deal with these walls by tricking a choice item to them. Signal Beam isn't really worth it because you have Weavile for Psychics, Grass types are already hit by Flamethrower, and most dark types are hit by Thunderbolt harder than Signal Beam. Try a set of Switcheroo / Thunderbolt / Overheat (or Flamethrower) / Hidden Power Ice. You can try either Specs or Scarf as an option, but Scarf is usually more harmful to walls than Specs is, but you may find yourself wanting a little more power.
On Terrakion I think you should try out a "Double Dance" set. It will give you more versatility based upon the team you are facing. Replace X-scissor with Rock Polish and change your item to a Life Orb. The idea is to Rock Polish against fast, offensive teams that apply pressure, and Swords Dance is for slower, Defensive teams. You can also keep your current set you have now also, as there is nothing wrong with it. You should also try Hidden Power Ice over X-Scissor, as even with a Hindering Nature I believe it 2HKOs most Gliscor, which walls your current set.
One last note, I don't know why you are in the Dreamworld metagame, because to me right now this team seems perfectly legal in Standard OU, unless I'm missing something or you just like to play Dreamworld.
Good Luck with the team!
