So, I was playing this game and we went into the summoning screen and saw this team and the first thing I thought was, "...Das OP". I was right. They destroyed us. They had SOOOO much damage and no matter how hard we hit, we couldn't kill any of them (except for Caitlyn, but she was just about impossible to get to!).
Now, I am no specialist on these champions and have no idea how to play them, in fact, the builds that I've presented are taken from other top rated guides (credits at the bottom), but I do know the strategies that they used, and the strategies that are open as well as each of their role on the team.
That being said, here are my musings, my thoughts, and a recounting of one of my experiences.

I just want to give a big thanks to the following for their contributions to this guide:

• Snowcherry for the overview and build guide on Caitlyn
  
• Shaxys for the overview and build guide on Garen
  
• Haxes for the overview and build guide on Swain
  
• Keels for the overview and build guide on Singed

Btw; the champion names are links to the awesome guides these guys posted (hint..hint...)

• Maokai-The jungler and traditional 'tank'. His main responsibility was to use Twisted Advance to guarantee kills during the laning phase, scout with Sapling Toss, and make it impossible to kill anybody because of Vengeful Maelstrom.
  
  
• Singed-Anti-escape artist and distraction. His wide array of slows and throw-backs made it impossible to move very far, meaning that escape was impossible once you were engaged. He is also Singed; meaning that he can take a lot of damage and dish it right back out, the whole time running you from one end of the map to the other.
  
  
• Garen-Main AD. Garen was the main physical damage dealer on the team.
  
  
• Swain-Main AP. Swain was the main magic damage dealer and was usually the main initiator of teamfights.
  
  
• Caitlyn-Long range pester and tower killer. Her main job for the whole campaign was to set down Yordle Snap Traps in bushes and then use Piltover Peacemaker and basic attacks to whittle us down from too far of a range to retaliate without meeting with Singed or the rest of the motley crew.

Each of the above mentioned characters fills a very specific niche in the team comp, however that is not to say that there are not other champions that can fulfill the same role.
For instance, it is very plausible to replace Swain with Cho'Gath at solo top or Caitlyn for ap Kog'Maw. However, this is the team comp that I saw run and so that is how I am going to report it.
Now, that we've established that, there are some champions that should not be replaced. For instance, the team does need a jungler, and Maokai does represent the best choice for this particular team simply because of his damage reduction, strong jungle, and early gank as well as his overall durability. Likewise, a strong damage dealer/damage taker like Singed is very necessary.
The next thing that needs to be acknowledged are support/tanks like Alistar or Taric. While it is true that they are both durable, neither one has the damage output to meet the requirements of this team. The reason that this composition works is because every member can both take damage as well as deal a significant amount. That being said, this role of champion lacks the damage output to add a strong edge to this team and so must be overlooked in favor of other candidates.

So, they ran a pretty standard setup for a higher ELO team, with the main difference being the characters that were used.

• They sent Maokai to the jungle where he started ganking around level 3 or 4. Twisted Advance into Sapling Toss and arcane smash just annihilated rooted targets with the help of allies. Then he would return to the jungle where he would later jump out somewhere else and repeat the tactic.
  
  
• They had Caitlyn at mid. This team does not have a real support role, but they do want Caitlyn to get farmed up, so the decision is to either send her mid, or have her 2v1 at top. So, Caitlyn went mid.
  
  
• They sent Swain to solo top. HE NEVER LEFT THE FREAKIN LANE!! EVER!! He would sit back and kill minions with Nevermove and when his health got low, he used Ravenous Flock to regen his health back.
  
  
• At bot, there was Singed and Garen. Ugh. Because both of them were so tanky, they could walk up and pester a little bit, and then retreat and even though we did more damage than they did, they could shrug it off while me and my partner could not. This continued until either Maokai ganked, or Singed used Fling to throw whoever he caught back to Garen, who made very short work.

We were getting our butts kicked in the lane, so we decided to change strategies by breaking out into teamfights because we figured that since we had a larger damage base, we could still take them down before they got farmed up enough to start dealing damage too. Well, we were wrong. Either Swain or Maokai would initiate. Swain would stand really far back and use Nevermove at the very edge of its range. Most of the time it missed, but the few times that it did, it was insta-death. 1 or 2 of us would get caught up while Caitlyn would stand near the back and take pot shots. Swain and Singed would immediately launch into the middle of the fight, Swain with Ravenous Flock and Singed with Poison Trail. Garen would use Judgment and just spin to win. After everyone was engaged, Singed took up the devious role of running around the small bunched up group of victims and use Mega Adhesive combined with Fling to send anybody foolish enough to think that they could run away back into the middle of the melting pot; and if he missed, Caitlyn and Ace in the Hole wouldn't. Maokai used Vengeful Maelstrom over the group for damage reduction and we just proceeded to die.
The other form of initiation was to have Maokai come toward us using Twisted Advance and then immediately throw down Vengeful Maelstrom and then have the rest of his team follow in using a similar method described above.

Anybody who has ever played as or played against a Singed knows that he is the best kiter in the game. He activates Insanity Potion and gets massively reduced damage as well as a really big speed boost. Well, this Singed would run up to the tower at mid around the 20-25 minute mark and start attacking it. Well, we attacked the son of a potion maker. He would then activate Insanity Potion and Poison Trail and run around our jungle. Everyone who followed was poisoned, everyone who ran around to intercept him was flung back into the noxious gas. None of us could really catch him, but we couldn't ignore him because he kept beating on our tower and everytime that we disengaged, he would just turn around and use Fling and proceed to kill us in a very Singed like fashion. Well, finally, we killed him. However this remark from the announcer was immediately met with "a tower has been destroyed!". While Singed has us locked up, the rest of their team by-passed all of the minions and was attacking the turret at either top or bot. Because every one of them except Caitlyn was very durable, they could take turns tanking the turret for the others while the lot of them took it down.

After this happened the first time, we were prepared for the second time; we thought. We sent 3 to deal with the new threat and kept 2 to fend off Singed. He tanked the tower, and the 2 champions long enough to do serious damage to the tower. Meanwhile, we showed up to a mini teamfight at bot or top and since they had taken turns with the turret, they were all healthy enough to dive us.

They had a jungler, in this case Maokai, meaning that unless a really good jungler who excels at counter-jungling is on your team, Maokai has primary control over buffs and dragon. He would actually come over and use a sight ward next to our buffs as well as theirs so that anytime that anyone went for one, their whole team was ready for us.
This combined with an effective counter jungling method made it very hard to make up experience lost in the laning phase. He did this by running through the jungle and killing every single one of our monsters except for one. This made sure that the minimum amount of exp and gold were available and made it so that the camp would not respawn until we found it and knocked out the last monster.

This team is obviously really tanky, so tank killing items like Madred's Bloodrazor or champions like Vayne tend to do well because the percentile damage from max health just naturally eats these champions; and items like Last Whisper or Void Staff cut through resistances so you can still damage them pretty hard anyway.
The biggest problem with this counter however, is that there is no way for a champion who can utilize Madred's Bloodrazor or for those high DPS champions like Vayne or Kassadin to get in close enough to deal damage. Again, these are all tanks or offtanks, each one with a powerful array of CC and durability. So while it is true that there are items and champions who are designed to cut these champions down to size, it is impossible to get to them to do it without being caught out of position and punished for it.

Overall, this is a pretty short guide, but it's an experience that I had and I can't get it out of my mind. I really hope to never see this team comp again in my life, however I don't think that it should be forgotten or hidden because it is such a powerful presence in the game.
For any information about the actual builds of the individual champions themselves, please refer to the respective guides that are presented because these are theirs, not mine.
That being said, gl and hf!

• Thanks to Snowcherry for her overview of Caitlyn
  
• Thanks to Shaxys for his overview of Garen
  
• Thanks to Haxes for his overview of Swain
  
• Thanks to Keels for his overview of Singed

Hey, the names of the champions are links again....8)