Lets rate this team. It looks decent, but I have some changes to make.
Let's rate!
The first thing is to replace Misdreavus with Mega -Sableye. This Pokemon is a staple on Stall teams for many reasons:
-Extremely Bulky (Srsly this thing doesn't die)
-Magic Bounce prevents Entry Hazards, Status, Taunt, Encore, the list goes on.
-Sets up all over many Pokemon
-Can choose not to mega-evolve first to retain Prankster
-Great typing (3 immunities, 1 weakness)
Here's the common Calm Mind set that induces all the rage quits:
Sableye @ Sablenite
Ability: Prankster ====> Magic Bounce
EVs: 252 HP/252 Def/4 SpDef
Bold Nature
-Will 'O' Wisp
-Calm Mind
-Recover
-Dark Pulse/Shadow Ball
Barring a critical hit, this thing can set up on many Pokemon, it is your anti-entry hazard, anti-taunt, win condition, spinblocker, answer to opposing Stall and overall annoyer all rolled up into one Pokemon.
The next thing I would suggest is to give Unaware Clefable a try as a cleric for your team. Assuming this is singles, Clefable has a much more useful ability in Unaware, which renders setup sweepers checked as Unaware ignores their boosts. This Pokemon is also a counter to opposing Mega Sableye that can easily set up all over this team.
0 SpA Aromatisse Moonblast vs. +1 252 HP / 0 SpD Mega Sableye: 120-144 (39.4 - 47.3%) -- guaranteed 3HKO
Even your best answer to it which is Aromatisse can only manage a 3HKO with Moonblast to +1 Mega Sableye. It can easily obtain a few boosts while recovering off the damage, and before you know it its pretty much over. Slowking can possibly phaze with Dragon Tail but it will take a ton from Dark Pulse regardless.
0 SpA Unaware Clefable Moonblast vs. 252 HP / 0 SpD Mega Sableye: 174-206 (57.2 - 67.7%) -- guaranteed 2HKO
Clefable is a much more stable answer as it can ignore the boosts from Mega Sableye and cleanly 2HKO it, while against Dragons it will ignore their Attack boosts from Dragon Dance.
Heres a set:
Clefable @ Leftovers
Ability: Unaware
EVs: 252 HP/252 Def/4 SpDef
Bold Nature
-Moonblast
-Wish
-Protect
-Heal Bell
I would change Forretress Nature to Impish, as it is not running any Special Attacks. Slowking can run a Sassy Nature as it is already extremely slow (Base 30 Speed lol) and help it to take Special hits better.
Other than that, the team looks really solid!
Threat Number 1
"#"Ragequit
But seriously, it renders Forretress completely useless (All your entry hazards get bounced back, lol rapid spin explosion), Amoongus can Clear Smog it but other than that it cant do much, Slowking can at most burn with Scald or phaze, Aromatisse can only 3HKO +1 Mega Sableye (Assuming it switches in on Calm Mind. Other than that its a 2HKO). Solved with the addition of Clefable, although even it wont enjoy a burn.
Hope I helped!