Well, first thing is, since your Ludicolo has Rain Dance, you should probably replace Thunderbolt with Thunder on Zapdos to work in conjunction with Rain.
And as for Aggron, he should not have a Hasty Nature, it gives him less resistance to things like Close Combat and he's still gonna be slow as hell. (eg. it's not worth it) and I think you should replace Aggron's Surf with Brick Break, (60 base Sp. Atk isn't really usable) that is, if you were only getting Brick Break for destroying screens, but even if you weren't, you should still get rid of Surf.
and give Gengar Dazzling Gleam instead of Brick Break, it still kills Dark-types and it uses Gengar's great Sp. Atk instead of Attack.
And for Muk, he should not have a Quiet Nature, because it's completely useless to him D: He should have something like Impish or Careful, preferably Impish because he's gonna hit hard with Earthquake :/ (had one before, he was mah boy. ;m;)
Overall, I think your team is relatively good, but like you said there are some obvious holes. :P oh yeah, I forgot to mention, your Gengar should probably have a Timid Nature.
Hope I helped! And if I didn't...well that sucks I guess XD