Too lazy to look for furai's post on him explaining why risking a game on will o wisp makes a team average at best.
		
		
	 
"The primary method by which an excellent Übers team deals with Extreme Killer Arceus must 
not  be through trying to burn it with the move Will-O-Wisp. Let's say there  is a team like mine which has Espeon, Multiscale Lugia with Toxic and  Whirlwind, as well as a physically defensive Groudon with Dragon Tail,  but one of its other members, say an Arceus-Ghost, just so happens to  know Will-O-Wisp. Trying to burn an Arceus-Normal with that Arceus-Ghost  as a last-ditch effort to stop it from sweeping after one's Lugia and  Groudon have been taken out would be fine. However, a team that relies  entirely on that Arceus-Ghost's Will-O-Wisp in order to stop  Arceus-Normal... in other words, a team which 
would be swept by  an Arceus-Normal if Arceus-Ghost fails to burn it before getting taken  out by it, cannot possibly be an excellent Übers team, because a team  whose sole answer to Extreme Killer Arceus is a Will-O-Wisp-reliant  Pokémon like Arceus-Ghost, Arceus-Steel, Arceus-Rock, and  physically-defensive Giratina is, by my judgment, a team that does 
not  have a counter or check to Arceus-Normal, and therefore automatically  fails, being an average team at best, since Extreme Killer Arceus is by  far the best Pokémon and most dangerous sweeper in the game. You may be  able to win many battles by shutting down the opponent's Extreme Killer  Arceus with Will-O-Wisp, while ocassionally having to use the move twice  against one that holds a Lum Berry, but climbing the ladder and  reaching #1 involves winning not just more than half the time, but doing  so 
consistently. If you just rely on Will-O-Wisp against  Arceus-Normal, you'll sooner or later find a battle in which your  Will-O-Wisp user gets taken out by the opponent's Extreme Killer Arceus 
before  you manage to burn it, and then get swept, and higher up on the ladder,  this will result in you losing a number of points which would require  ten or more battles to make up for... assuming Will-O-Wisp doesn't miss 
again within those ten battles and resulting in you falling even  lower on the ladder. Also keep in mind that the probability of two  Will-O-Wisps hitting in a row, which is necessary to burn a Lum Berry  Arceus, is only 56%. This is one of the primary reasons why I do not  consider many, if not the majority of Übers teams (including many of  which created by myself in the past), to be truly excellent teams."
^Hack He Must posted this, not Furai. Basically, if Will-O-Wisp misses,(which has a chance to miss higher than that of a 100% accurate attack missing Sand Veil Garchomp and equal to that of a full paralysis) Arceus or Excadrill or Kabutops can sweep a team.
My thoughts on the CCAT: From what I have read, it seems that the likely picks are as follows: 
Rayquaza, Giratina-O, Palkia etc. This is not a good idea since this is stacking Dragon weaknesses. Since an offensive team will be used, there will be no room for a Bulky Steel Type as it kills the momentum. The only possibly viable steel type is Genesect which is frail and can switch into Dragon attacks only once.
I do not like Rayquaza. It is frail, SR weak, slow, and easily revenge killed. It is not a counter to weather sweepers, it is only a check. Since this team is weatherless, it will be weak to Kingdra(the team is going to stack Dragon types and Genesect can't switch into it). I do not understand what Rayquaza does that Latios does not do.
I think Deoxys-S should be the lead used for the CCAT as it is the most consistent lead and it does 
not have to play a mindgame with set-up sweepers. Back in DW Ubers, I used a Custap Berry Forretress lead which was very inconsistent. Why? Because it was very common and most people figured out how to beat it - attack first to break Sturdy and then KO it. Instead of trying to use Rapid Spin, which is unreliable, the CCAT could just include Pokemon that can kill hazard setters quickly. Example: Latios.
I am going to nominate Substitute + Nasty Plot Darkrai again. Dark Void allows it to put one member of a defensive core to sleep, enabling the rest of the team to find an opening.
                                                                  
		
		
	
	
Artemis (Darkrai) @ Leftovers
Trait: Bad Dreams
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature
IVs: 0 Atk
- Dark Void
- Substitute
- Dark Pulse
- Nasty Plot
A Darkrai moveset I first used in puregenius's 
The Requiem,  and also currently use in another team I commonly battle with. Despite  its lack of coverage moves, this Darkrai is an unbelievably dangerous  offensive threat judging by my own experience from both using and facing  it, as the combination of Substitute and Nasty Plot can very easily  catch people off guard, since Darkrai rarely uses both of these moves at  the same time. If one somehow manages to set up a Nasty Plot while  having a Substitute up (which isn't too difficult with some intelligent  application of Dark Void, Substitute, one's own prediction skills, as  well as the utilization of people's tendency to not expect Darkrai to  have both Nasty Plot and Substitute simultaneously), one can pretty much  expect 
Artemis to be able to at least devastate a large portion  of the opponent's team before going down (and very likely, the opponent  may even need to sacrifice a Choice Scarf-holding Pokémon or a user of a  priority move such as their Extreme Killer Arceus in the process of  breaking 
Artemis's Substitute, and being able to eliminate such  Pokémon in the opponent's team pretty much for free is always helpful),  thanks to its high Speed and incredible power after just a single Nasty  Plot. Against some teams, it can even get a free Substitute on the turn  in which the opponent switches to their Espeon or Xatu expecting a Dark  Void.