Hi :) To start off, I would like to say that I'm rather new to the competitive battling community and competitive battling in general. This is the first team I've built, and I've been using it to quite good success on the Wi-Fi servers, but I'm not one to say that it's without it's flaws. I'm intending to go to Worlds (grinders), and am just looking for general advice on this team to help it do better in the competitive environment. The team is built around Tailwind support, with Whimsicott+Terrakion as leads and Thundurus and Conkeldurr as attackers. I am currently in the process of choosing the final two team members and would appreciate suggestions on what to choose if possible :)
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Leads:
*~Terrakion~*
Nature: Jolly
Item: Life Orb
Ability: Justified
EVs: 4 HP/252 Atk/252 Spd
-Earthquake
-Close Combat
-Rock Slide
-Protect
A typical partner to Whimsicott, thanks to the ability to heighten it's attack power massively thanks to Beat Up and boost it's speed with Tailwind. First turn I always want to use Protect while Whimsicott uses Tailwind, then next turn (Whimsicott will most likely have survived thanks to Focus Sash) use Beat Up on Terrakion to start OHKOing with Earthquake/Rock Slide. Earthquake/Rock Slide/Close Combat are there for coverage. I'm thinking of changing Rock Slide to Stone Edge, but hate the accuracy and don't think that I really need the extra power.
*~Whimsicott (M)~*
Nature: Timid
Item: Focus Sash
Ability: Prankster
EVs: 252 HP/4 SpD/252 Spd
-Tailwind
-Beat Up
-Taunt
-Protect
My other primary lead, this one is to purely set up and stop Trick Room thanks to priority Taunt. As I described above, Tailwind and Beat Up are there to set up Terrakion, while Protect is there to give it a turn to live if needed. Focus Sash is there so that Whimsicott gets to attack with Beat Up/Tailwind on the second turn almost 99% of the time, unless my opponent ends up attacking it twice in one turn.
Attackers
*~Thundurus (M)~*
Nature: Timid
Item: Electric Gem
Ability: Prankster
EVs: 4 HP/252 SpA/252 Spd
-Thunder Wave
-Taunt
-Focus Blast
-Thunderbolt
This is one of my attackers I use primarily after Terrakion gets KOed, but it can be also used as a lead to spam Thunder Wave and use Taunt. Prankster allows both of these to hit first, so it's great to cripple attackers that rely on Speed with Thunder Wave, as well as Trick Room users thanks to Taunt. Focus Blast and Thunderbolt are my attacking moves (obviously), but I'm really looking for something to replace Focus Blast as I hate the low accuracy... :/
*~Conkeldurr (M)~*
Nature: Adamant
Item: Flame Orb
Ability: Guts
EVs: 4 HP/252 Atk/252 Spd
-Hammer Arm
-Mach Punch
-Rock Slide
-Protect
The team's other main attacker, this one boosting it's attack thanks to Guts+Flame Orb and then hitting heavy with STAB Hammer Arm, as well as Rock Slide for extra type coverage. Mach Punch is an amazing attack, allowing me to freely KO things that have been heavily damaged by Terrakion/Thundurus and aren't immune to it. Protect is to stall for Flame Orb.
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And... That's all. I don't expect this team to be great at all and I know it probably has lots of problems, but I'm just looking for advice on what to add/change to make it better.
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Leads:

*~Terrakion~*
Nature: Jolly
Item: Life Orb
Ability: Justified
EVs: 4 HP/252 Atk/252 Spd
-Earthquake
-Close Combat
-Rock Slide
-Protect
A typical partner to Whimsicott, thanks to the ability to heighten it's attack power massively thanks to Beat Up and boost it's speed with Tailwind. First turn I always want to use Protect while Whimsicott uses Tailwind, then next turn (Whimsicott will most likely have survived thanks to Focus Sash) use Beat Up on Terrakion to start OHKOing with Earthquake/Rock Slide. Earthquake/Rock Slide/Close Combat are there for coverage. I'm thinking of changing Rock Slide to Stone Edge, but hate the accuracy and don't think that I really need the extra power.

*~Whimsicott (M)~*
Nature: Timid
Item: Focus Sash
Ability: Prankster
EVs: 252 HP/4 SpD/252 Spd
-Tailwind
-Beat Up
-Taunt
-Protect
My other primary lead, this one is to purely set up and stop Trick Room thanks to priority Taunt. As I described above, Tailwind and Beat Up are there to set up Terrakion, while Protect is there to give it a turn to live if needed. Focus Sash is there so that Whimsicott gets to attack with Beat Up/Tailwind on the second turn almost 99% of the time, unless my opponent ends up attacking it twice in one turn.
Attackers

*~Thundurus (M)~*
Nature: Timid
Item: Electric Gem
Ability: Prankster
EVs: 4 HP/252 SpA/252 Spd
-Thunder Wave
-Taunt
-Focus Blast
-Thunderbolt
This is one of my attackers I use primarily after Terrakion gets KOed, but it can be also used as a lead to spam Thunder Wave and use Taunt. Prankster allows both of these to hit first, so it's great to cripple attackers that rely on Speed with Thunder Wave, as well as Trick Room users thanks to Taunt. Focus Blast and Thunderbolt are my attacking moves (obviously), but I'm really looking for something to replace Focus Blast as I hate the low accuracy... :/

*~Conkeldurr (M)~*
Nature: Adamant
Item: Flame Orb
Ability: Guts
EVs: 4 HP/252 Atk/252 Spd
-Hammer Arm
-Mach Punch
-Rock Slide
-Protect
The team's other main attacker, this one boosting it's attack thanks to Guts+Flame Orb and then hitting heavy with STAB Hammer Arm, as well as Rock Slide for extra type coverage. Mach Punch is an amazing attack, allowing me to freely KO things that have been heavily damaged by Terrakion/Thundurus and aren't immune to it. Protect is to stall for Flame Orb.
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And... That's all. I don't expect this team to be great at all and I know it probably has lots of problems, but I'm just looking for advice on what to add/change to make it better.
Thanks,
~Glaciate
~Glaciate