We'll also need items, btw. :3
For Reuniclus you really need Shadow Ball, while it has lower power (@ lvl 100), it's actually a lot more useful, offering a possible special defense drop. Replace Thunderbolt with Trick Room since you can OHKO water and flying types w/ Psyshock anyway. Plus with a -speed nature, then Trick Room is used all the better. If not just go for Modest if you wanna use Calm Mind instead.
On Delcatty, Assist isn't really the best since it chooses an attack at random, instead go for something status-based + STAB. So... since you also need a STAB attack, go for Return or Body Slam to either hurt the opponent or paralyse them. Dig isn't that great since opponents can switch, etc ;x So yeah, Earthquake is better, but unfortunately Delcatty can't learn it. Sadly though, ground coverage doesn't really help it. You could go for support with Heal Bell aaand then go for Thunder Wave + Sing, or Wish, depending on how you want to support your team. Declatty is a bad Pokemon anyway, so.
Latias is defensive mostly, so if it's going for a Dragon attack, then go for the second strongest (Dragon Pulse) on the special side. Fly = for in-game purpose yeah I get that. Sucker Punch doesn't really help it, instead fit Calm Mind on somewhere so it can become more offensive & boost Dragon Pulse. Aerial Ace doesn't help Latias at all, if you wanna make it defensive though, go for Recover/Wish and Reflect to support your team & you when setting up.
Palkia really needs a dragon STAB, go for Dragon Pulse or Draco Meteor for more power, since Surf isn't good enough to hold you over STAB-wise. Thunder or Fire Blast = great for coverage and Spacial Rend could also be good too.
Same goes for Dialga, it also really needs Fire Blast and Thunder for coverage. Ice Beam and Blizzard, not really, since you already have Dragon Pulse and Roar of Time isn't really that useful. Don't know why you're using HP ghost, but I guess if you wanted, you could use Stealth Rock and use Roar on Latias (instead of Reflect) to accumulate damage on the team of the opponent.
Aaand Beheeyem isn't really the greatest Pokemon so there's nothing I can really suggest. :( Good luck though!
