Updated on Dissidia Arcade with character trailers of Shantotto and Vaan as well as video descriptions of their beginning movesets (Japanese only, as usual).
Also, for those who care, I've gone out of my way to explain the full gameplay of 3v3 in Dissidia Arcade through a written breakdown:
If it hasn't been obvious by now, this game plays radically different from the previous Dissidia games.
1) Gone are the RPG-centric elements such as equipment, accessories, battlegen, and the like that buffs your character stats. Everyone has a fixed initial Bravery of 1000 points and the standard HP total of 3500, with a damage ratio unique to each character.
2) Matches now have a time limit. Furthermore, players can either control each member in a party of three or control one character with two of the others being AI-controlled.
3) Unlike the previous games, you are now limited to one HP attack and seven Bravery attacks at a time. For Bravery attacks, you can equip 3 ground attacks, 3 aerial attacks, and 1 used specifically during a dash.
4) Speaking of dashing, there is now a dash gauge that depletes when you use it, which now makes advanced movements in the game more strategic than ever. What's more, the chase mechanic has understandably been removed from the game completely, as this guessing mechanic would break the flow of the already hectic combat.
5) Defending in Dissidia Arcade is completely different from the previous games. As opposed to timing the first hit of the bravery attack and parrying it to gain frame advantage, you now block an entire string of bravery attacks without taking damage with a bubble shield akin to Super Smash Bros (which weakens and breaks after prolonged use in the same fashion). At the same time, you get knocked back the same way you would if you were hit by the bravery attack.
6) In 3v3 match play, the match is determined by the team that has the most Global HP, which is the blue and red bar the party shares on the top left broken into five segments (Blue for one team, Red for the other).
If an individual party member is KOed, they aren't necessarily eliminated from the match, and can be revived. However, it permanently effects the team's Global HP. Regardless of who gets knocked out, 5 KOs mean the party loses the match.
7) Targeting is similar to previous Dissidia games, except now you can choose which opponents to target. The indicator is where the blue line points. Be careful though, if the line turns red, it's a sign that you're in danger of being attacked.
8) The EX Gauge and the fixed status buffs for EX Mode -as well as the EX Burst and the EX Revenge breaker associated with it - are now gone. Replacing these features are three EX Skill components, and two can be customized while one is unique to the character.
For example, Terra and Zidane have Trance as their unique EX Skill, but you can customize two other general EX Skills to your liking. The EX skills are automatically made available as time progresses in the match, and have a significantly long cooldown period once used... in particular, the character's unique EX Skill takes the longest to recover.
9) The white meter above the two Global HP meters is the Summon Gauge, which builds up when you either deal damage to the opposing team, then hit the Summon Crystal that appears in the field, get the Summon Icon, and then channel a summon without taking a hit. The team player that summons first gets assistance for the whole team from the selected Eidolon, though it acts on its own.
Understandably, this replaced the individual EX Bursts of the previous two games in order to prevent the flow of the game from being broken.