SET REVIEW!
As a whole, Double Crisis is surprisingly good. It features great artwork and 2 fun new archetypes. As for how strong Team Magma and Team Aqua are, I'm not that sure...
Team Magma
Misc Tools
Zangoose is the heart and soul of Team Magma. It is an absolutely incredible starter for a match, because it preps your bench and has a strong follow-up attack. The Fighting Weakness DOES make it susceptible to Landorus-EX donks, but that it moreso a precaution for specific match-ups.
Camerupt is a strong 2-2 line or 3-3 line utility for Team Magma to work with. It draws in Energy, which can then be moved with either Energy Switch or Claydol. The combo isn't nearly as viable as things like Bronzong, but it is pretty cool, and might even work in other kinds of archetypes.
Magma Great Ball is cool, but kind of redundant for this deck. Ultra Ball is the better option, because you already get Basic Searching help with Zangoose.
Courtney & Tabitha are pretty strong on paper, but I feel that just a single copy is all you need for the deck. The only time it becomes super useful is when 1 of your Camerupt's or Claydol's get Lysandre KO'd, or when you need to rebuild an Aggron.
Team Magma Grunt isn't really that good for our current format. Don't use it.
Magma Pointer is really sad, honestly. The only reason to use it is to set up an opponent for a Magma Quake or Rock Storm. Besides, Forretress and Golbat/Crobat do better jobs of damage drops.
Team Magma's Hideout is the last tool that Magma gets at their disposal, and it's honestly strange. While it is great for setting up for Magma Quake and Rock Storm as well, I think that Scorching Earch might be the overall better choice for a Stadium, since you get Camerupt/Claydol synergy.
Groudon EX variants
Groudon-EX is a better attacker than Kyogre-EX, and the tools it has going for it make it much stronger. It gets Energy acceleration with the help of Camerupt, and then all it takes is 2 damage counters on your opponent and a Magma Quake to hit 180. Probably the most viable of the attackers.
Aggron variants
I really like this card. I know it won't become a metagame-stay, but Aggron is unique because of how it gets 2 fun archetypes to go along with it. The first being a combo with Camerupt. While this does take several Stage 1's in play, the payoff is certainly strong. The second combo is with Forretress, which allows you to do 120 to the Active (with Fighting modifiers) and 30 snipe to the Bench. Both are pretty strong options!
Mightyena variants
I don't think this card is very good. At all. Magma Mightyena is only viable for Aqua Matchups, but you won't even need it for that because you're better off just using Groudon, Aggron, or even Zangoose!
Team Aqua
Misc Tools
I like how Team Aqua has a bit more of a variety in the choices of what to work with. The archetype probably isn't as strong as Magma, but I do enjoy all the little tricks you can pull with it.
Sharpedo is the signature 2-2 line that you'll need in every Team Aqua deck. A free search once per turn outclasses Aqua Ball by a MILE, and you can stack it. You could search for another Sharpedo, then use it again to search for 1 more Aqua Pokemon. Then, you still get 2 free searches the following turn. The free retreat is the icing on the cake for Sharpedo, because you can promote it whenever your Active gets Knocked-Out.
Muk is really only a huge card when playing Kyogre-EX. The extra Retreat only helps when using a Retreat-based attacker, and the only merit it gets above Jellicent is that it's Sharpedo searcheable.
Aqua Great Ball is pointless. Just use Sharpedo & Ultra Ball.
Aqua Defuser is stronger than Magma Pointer, and pretty cool. Confusion and Poison off of 1 Energy isn't the craziest thing ever, but it does help set up for the chances where you need to use something like Muk or Seviper for attacking.
Matt & Shelly is pretty much what can be summed up as 'Aqua-smith'. You'll probably have to run a pretty heavy amount of them in your deck to make them worth the time(2-3), but every little Energy does help.
Team Aqua's Hideout is only helpful if you're using Kyogre-EX. Otherwise, the 1 extra Retreat is usually an average addition, made even worse when taken into consideration that this won't affect any Pokemon that has no Retreat or a Float Stone.
Kyogre-EX variants
The reason why I feel that Kyogre-EX isn't as strong as Groudon-EX is because of how many bad match-ups it gets. Attacks based on Retreat Costs are usually strong when they're used as Type Advantage attackers (Plasma Garbodor, Beartic), but Kyogre-EX fails in that department because of how it needs to be the HEAD of a deck. Lots of decks run 1 Retreat cards as the focal point of a deck(Virizion/Genesect being the worst matchup), and even with Muk boosts and Aqua Hideout, Kyogre will only hit for about 140 on average. While there always are the strong matchups where you can hit for nearly 200+, there really is too much going against Kyogre-EX to make it the king of our current format.
Walrein variants
While sniping 2 Pokemon for 80 is strong, Walrein falls short because of the hefty Energy cost. Besides, 80 isn't the most jaw dropping amount for a snipe, especially considering that Mr Mime is still in the rotation. Power Blow is average as well, doing a pretty moderate amount. The nice thing about Walrein, despite all of those flaws, is that the discard effect from Dual Blizzard is ignored by discarding Aqua Energy.
Seviper variants
Getting special conditions on your opponent is MUCH easier than it sounds because of Hypnotoxic Laser and Malamar-EX, and being able to auto-discard off of an attack is pretty useful. It avoids the usual coin-flip problem, and unlike Mega Lucario-EX and Samourott BCR, Seviper is a 2 Energy Basic. Seviper isn't really something I would use as the head of a deck because of the low damage output, but it is a very cool card for creative games.
Mightyena variants
I gotta say, this is probably the only Mightyena card in existence that I like. Even with the strong reliance on luck, Mightyena can be quite fun to use for pleasure. Too bad you'll have to use Trick Coin, because using Victini means you get 1 less spot for a Team Aqua Pokemon to power up your coin flips.