Your team is definitely unbalanced, with 3 Flying types and a really weak Pokémon before it evolves, Deino.
Changes are in italic.
Surf/Waterfall - Depending on the stats of Samurott, Surf or Waterfall is better than Aqua Tail.t
Ice beam - Good Coverage move, better than revenge.
Please remove Unfezant and Deino. Unfezant is not great in the League and Deino is simply a burden for your team, you can have a Hydreigon after the league, not before.
I suggest you to try Sigilyph, his Flying and Psychic typing will help you with Marshall.
Sigilyph, as a replacement for Unfezant.
Ability :- Magic Guard
Held item :- Life Orb
Air Slash - Great with Sigilyph’s nice Special Attack, can make flinch.
Psychic - Very nice Psychic type move.
Energy Ball - Coverage move.
Shadow Ball Coverage.
So yeah Sigilyph is really nice for the League, with Magic Guard, all his moves can be boosted with Life Orb without taking damage.
As I said, Deino will not help you during the League.
Krookodile, as a replacement for Deino.
Ability :- Moxie
Crunch/Foul play - Crunch is better since it’s more reliable than Foul Play, in case you opponent’s got low Attack.
Earthquake - Self Explanatory
Rock Slide - Coverage against Bug types and Ice types.
Dragon Claw - Coverage against dragons.
Archeops is a Sweeper, so it has low Defense and Special Defense. Keep it if you want, but give him Stone Edge and U-turn, and also Fly.
So, here’s the team I think would be nice.
Archeops If you want to replace it as well, just put a comment and I’ll send you a moveset for another Pokémon.