Other than hitting Dragons, Dazzling Gleam isn't doing much for Jellicent. The threat of Scald burns is generally enough to deter most physical Dragons from switching in. Jellicent's physical bulk isn't that good, really, meaning that it can't really make use of Rocky Helmet; that item is better suited for physically bulky Pokemon. A better take on specially defensive Jellicent is this:
-Scald
-Hex/Shadow Ball/Taunt
-Will-o-Wisp
-Recover
Nature: Calm
EVs: 252 HP/212 SDef/44 Spe
Item: Leftovers
Ability: Water Absorb
Co***rigus is doing too much at once. Trick Room sets should use an offensive set and spread to make the most out of the 5 turns. A better defensive Co***rigus is:
-Toxic Spikes
-Shadow Ball/Hex
-Will-o-Wisp
-Pain Split/Snatch
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
This team lacks powerful attackers outside of Doublade. Dusknoir isn't one of those attackers because it lacks a good Ghost STAB. Have you even considered Gengar or Chandelure?
Gengar:
-Substitute
-Shadow Ball
-Will-o-Wisp
-Taunt/Disable/Sludge Wave/Sludge Bomb
Nature: Timid
EVs: 28 HP/148 SAtk/80 SDef/252 Spe
Item: Black Sludge
or
-Hex
-Taunt
-Will-o-Wisp
-Substitute/Sludge Bomb/Sludge Wave
Nature: Timid
EVs: 8 HP/248 SAtk/252 Spe
Item: Black Sludge
or
-Shadow Ball
-Sludge Bomb/Sludge Wave
-Focus Blast
-Taunt/Destiny Bond
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb
Chandelure:
-Fire Blast
-Shadow Ball
-Hidden Power (Fighting)/Energy Ball
-Trick/Energy Ball
Nature: Timid/Modest
EVs: 4 Def/252 SAtk/252 Spe
Item: Choice Scarf/Choice Specs
Ability: Flash Fire
or
-Shadow Ball
-Fire Blast/Will-o-Wisp
-Substitute
-Taunt
Nature: Modest
EVs: 160 HP/156 SAtk/192 Spe
Item: Leftovers
Ability: Flash Fire
Despite its offensively-leaning stats, Trevenant is better off using defensive spreads, given how it relies on defensive berries to function:
-Substitute
-Leech Seed
-Will-o-Wisp
-Phantom Force/Horn Leech
Nature: Careful
EVs: 252 HP/4 Def/252 SDef
Item: Sitrus Berry
Ability: Harvest
or
-Horn Leech/Shadow Claw
-Will-o-Wisp
-Leech Seed
-Rest
Nature: Careful
EVs: 252 HP/4 Def/252 SDef
Item: Lum Berry
Ability: Harvest
Under normal circumstances, Super Size Gourgeist now outclasses Trevenant, as it has better bulk to match its good support move pool:
-Will-o-Wisp
-Leech Seed
-Synthesis
-Seed Bomb/Shadow Sneak
Nature: Impish
EVs: 252 HP/160 Def/96 SDef
Item: Leftovers
Ability: Frisk
While it seems tempting to have Doublade use Swords Dance to break things down, it has a tendency to get itself worn down fast in the process, given its bad Speed:
-Gyro Ball
-Toxic
-Rest
-Sleep Talk/Sacred Sword/Pursuit
Nature: Sassy
EVs: 252 HP/4 Atk/252 SDef
Item: Eviolite
Oh, but that does remind me(and sorry for the double post). But on this team, I have considered replacing someone with Drifblim JUST so that I can have some Defog Support. Have any suggestions for that or how I can maybe incorporate it, or how much of a good idea that is?