To start it off, you're team has common weaknesses to Flying, Poison, Rock, Electric and Fairy, which are common move types used in VGC. Offensively, your team doesn't have enough type coverage. The absence of Electric attacks, Rock attacks, and Poison/Steel attacks will make it hard to deal with common threats like Milotic, Suicune, Charizard Y, Talonflame, Sylveon and Mega Gardevoir.
The next flaw is that your team mates have common items. VGC's item clause clearly states that you can only have one of each item on your team.
And another thing, why do all your Pokemon have 80 EVs into HP and 180/248 in another stat?
The Mega Slowbro set isn't bad, but the EVs don't give you the flexibility to survive certain attacks such as Thundurus' Thunderbolt or Ludicolo's Giga Drain. A set like this achieves that and more
Trick Room allows Mega Slowbro to always be the first thing that moves the next turn, Slack Off for obvious HP recovery and Scald/Psychic for STAB. You won't need Fire Blast over Psychic in most cases since Psychic will be doing more neutral damage and Fire Blast only checks around 5 Pokemon in the format. You can always switch out Trick Room for Calm Mind if you plan to run slower Pokemon.
This Whimsicott set is really...well it can't work in VGC. Tailwind works but Mega Slowbro can't really take advantage of it with its low speed, Toxic stalling is impossible in a VGC setting and Whimsicott doesn't have the most amazing Special Attack stat. To be honest, I would recommend scrapping Whimsicott since it doesn't do much supportively for Mega Slowbro other than the fact it has Taunt and Trick Room.
Amoonguss would make a better fit here since it can redirect attacks that hit Slowbro for super effective damage.
Here are my recommendations for this team
Your team would look like this based on my recommendations:
The team you have hear is unstable seeing as how common VGC Pokemon cut through it with ease, Pokemon like Landorus-T, Sylveon, Kangaskhan, Salamence etc gives this team a hard time. The EV spreads aren't functional and the move set choices drive it down to rubble. Not a bad start for a team but you need to consider things like Speed Controlling and EVing, managing your weaknesses and making the team synergize instead of conflicting with itself.
![[Image: 080.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/080.gif)
![[Image: 547.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/547.gif)
![[Image: 468.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/468.gif)
![[Image: 560.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/560.gif)
![[Image: 461.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/461.gif)
![[Image: 485.gif]](http://pldh.net/media/pokemon/gen6/xy-animated/485.gif)
