At first, I thought this was an NFE team, until you added Miltank. However, this doesn't really change the fact that most of your pokes are slow and frail (with the exception of Miltank, and maybe Tentacool on the special side). A decent physical wall can stall most of your team as well. Weezing can tank your attacks and cripple most of your team with Will-o-wisp and Clear Smog. Without Eviolite, Lampent can't really switch in to Sludge Bomb repeatedly (especially with entry hazards).
Three Choiced Pokes are also relatively easy to play around. Tangela can also tank attacks and Knock Off your important items. As for offensive threats, other than the ones already mentioned, Piloswine can handle your entire team! On a more serious note, a combo of Ludicolo and Nasty Plot Jynx (rain teams in general actually) shreds through your entire team with little trouble.
I would replace either Dragonair or Zweilous with either Special Defensive or Choice Specs Altaria. Specs Altaria with Cloud Nine works well with the offensive nature of your team, weakens weather teams somewhat, and devastates physical walls with powerful Draco Meteors.
Scarf Sawk over Lampent sounds like a good idea as well, since your team is pretty slow. If you add Quagsire as well, you can ditch Toxic on Miltank for Body Slam or Earthquake to prevent it from being Taunt bait. Hope this helps!