Disclaimer: I make several assumptions in this review
First of all, your EV setup is a bit confusing. Because you label the special stats as sp.atk and sp.def, I'm assuming spd refers to speed (even though, usually, SpD stands for sp def and Spe is speed).
Let me start this review with a compliment: Type-wise, this team is fantastically well rounded. Only two types, fighting and poison, are supereffective on more than one pokemon, and you have other mons that resist them to help balance it out. Honestly, I've made very few teams as defensively sound as this. Great job in that regard!
But, unfortunately, this team is littered with a horde of other problems. Half the natures are either counterproductive or don't do anything (For future reference: never use Serious, Quirky, Hardy, Docile, or Bashful Natures; they don't do anything), several EV spreads are sloppy, and moves that lower your opponent's stats aren't the best investment of your moveslots; it's much better to raise your own stats than lower your opponent's because they can just switch out and nullify the move.
However, a lot of things suggest that these are all in-game, rather than Smogon (an online simulator). I can respect that, and it does make some things more understandable, if not entirely excusable. Okay, here's a case-by-case breakdown:
Good EV spread, good nature, bad moveset and item. The mean look / perish song strategy undermines this pokemon's potential. I would go full fast special sweeper with it. Here's some suggestions for a moveset I would use:
- Charge Beam / Calm Mind (I would do c-beam, because it has a 70% chance to raise spA, but calm mind is respectable as well)
- Shadow Ball (STAB)
For the last two, you have some great coverage options with Dazzling Gleam and Power Gem, but, depending on the rest of your team, Psychic or Energy Ball could be good as well. Thunderbolt is also an option if you end up not going for Charge Beam, and, if you're willing to sacrifice a moveslot, Destiny Bond is a strong option with Mismagius' speed.
For the item, I would do Life Orb, Choice Specs, or Choice Scarf.
This... oh. He doesn't have enough base speed to justify 252 speed investment, especially with that quiet nature. And he has two stat-dropping moves the opponent can nullify by switching. Honestly, I don't think I've ever seen a skuntank used competitively; it's base stats are a bit lackluster, especially with other poison/dark types with better stats out there. I would replace this guy with one of the aforementioned p/d types. Here's what I suggest:
If you want a tank, Alolan Muk is your best option. You could run it with curse, if you want to be able to dish out some damage, or you could go stockpile, if you want to tank as much damage as possible. Additionally, if evasion isn't banned wherever it is you're battling, it also gets access to minimize. For the item, you could either give it black sludge, or, if its ability is gluttony, you could use aguav/figy/iapapa/mago/wiki berry.
If you want a bulky sweeper, Drapion has some rather frightening potential. Without any modifiers, its attack is just okay, but, use a Swords Dance, and you have an insane attack stat. Additionally, it has some impressive coverage options such as Earthquake, Brick Break, Iron Tail, Aqua Tail, Rock Slide, the list goes on. Plus, Sniper ability and Razor Fang for your item, and this guy's set.
This is the best set you have. Good EV spread, good nature, decent moveset, I personally wouldn't use that item, but it's still viable. The biggest thing that stands out is Flash. I would replace that with a fire attack, to counter steel and poison types, who can't be toxic'd. While ground is conveniently supereffective on both, if you run into a flying type or otherwise airborne foe, you'll have no choice but to switch. For this reason, I suggest Hidden Power Fire, being the only fire type attack umbreon can learn. However, if you can't get access to the right hidden power, you could also possibly run mud-slap. I know, it goes against what I said with both the type and the "don't lower the opponent's stats" thing, but, at the very least, it's better than flash. I will also suggest possibly replacing protect with substitute. Honestly, this is less of "substitute's better than protect" as it is "here's something you might want to consider."
For the item, I would give it leftovers, and, if I could make one small tweak to the EVs, move the 4 you have in speed to special attack.
This one confuses me. The first thing I see is Belly Drum, Sitrus Berry, and Unburden. That's a good combo! Then I see Play Rough and I think, "yes, that's a good STAB move". And then there's Protect. I mean, I guess Protect can be useful on anything to an extent, but sometimes, it's not useful enough to justify it taking up one of your moveslots. And then RAIN DANCE?!?!! Just... What? Replace those last two moves with other strong physical attacks. Unfortunately, Slurpuff doesn't have the best movepool, so your best options, hands down, are Drain Punch and Return, possibly Facade instead of Return if you're worried that you might get burned. Put full 252 EV investment into speed, and, if you don't mind putting in the work to get another one, Jolly nature.
Technician isn't a hidden ability; If possible, I would breed another so that you can have technician, as well as a Jolly nature. The EVs are good, the only other thing I would suggest is to give him a metronome (not the move; there's an item called metronome). I've run this moveset on other pokemon before and I can say from experience, metronome is the single best item for this strategy.
Pretty much the exact same situation as Slurpuff, except my reaction was "This again?" rather than "Good idea, bad execution." Because Slurpuff already runs the Belly Drum strategy (and can do it better because of unburden), I would suggest replacing azumarill altogether, preferably with some sort of special sweeper (I generally like to split my teams up into two physical sweepers, two special sweepers, and two tanks. But that's just what I like to do; I'm not saying it's the best way to break down a team). If you must go with defensive Belly Drum sweeper, however, here's my suggestion:
At first I was going to say get one with Huge Power if possible, but, now that I'm looking at it, Thick Fat might indeed be the better option, because at +6 atk, you're going to OHKO everything anyway, so let's get a defensive ability. Good call there. Helping Hand makes me think that this team is intended for doubles (which I suppose would explain Slurpuff's Rain Dance as well). I would not recommend doubles for your first competitive team, especially since the rest of your team doesn't particularly scream "doubles." If this was your intent, I would recommend you learn the competitive ropes in singles before diving into doubles. (Got off track there, sorry) Azumarill has decent coverage, with moves like Superpower, Iron Tail, and Play Rough, and it can have priority with Aqua Jet.
Here are some other suggestions if you want to replace Azumarill:
Primarina and Tapu Fini have the same types as Azumarill, making them obvious choices, but, honestly, I would instead recommend Mega-Blastoise (or just regular Blastoise, if you don't have the mega-stone). It's got insane bulk, and even more insane SpAtk, as well as some decent coverage. I would use Scald as this guy's water-type attack, as well as either Blizzard or Ice Beam, as well as an Aura Sphere (it gets a 1.5x boost from m-blastoise's ability). Feel free to get creative with the last moveslot.
Well, that was a lot. One last note: if you don't already, Smogon's Showdown! battle simulator is a great place for testing teams before committing the time it takes to make the team in-game.
Hope this helps and happy battling!