Right now, I can tell you're going to have problems if someone comes in with Ice Beam, considering one of your Pokemon is 2x weak to Ice, while two are 4x weak to it. I would take out either Dragonite or Salamence (because they really do function essentially the same way, and Salamence does it better with Intimidate and generally better stats) and replace it with something else. (I really can't help you decide what to replace it with, considering I don't know what moves your Pokemon have and therefore don't know how your Pokemon function or what types they can cover. I can assume by their standard sets, but you really could've given them anything.
Also, personally, I think there's better Psychic-types out there than Exeggutor. There's better Grass-types, too, but still. I'd say maybe, if you're going for a standard set with Leech Seed, you could maybe consider replacing it with an Alakazam or Espeon with Calm Mind. Espeon's a bit easier to get, and it has the benefit of learning Baton Pass, which means if you're in a jam with Espeon, BP those Calm Minds to Salamence (if Salamence has a special set), Gengar (same), or Lapras to make full use of it.
Also, Espeon and Alakazam's stats > Exeggutor's. Particularly in the departments of Speed and S Attack.
Hope that helps!