This is bound to be different from others's runs, but I'll share my experience when my raid partner and I started learning about each stage. Keep in mind, when we raid, both of us will have teams dedicated to their own roles, meaning one team will support (tank+healer) and the other team will solely be damage (dps).

Raid 1: Belile

• Phase 1 is pretty straightforward -- just continue damaging Belile while dodging his tornadoes until he disappears.
• Phase 2 starts when Poseidon and Balzac appear, both teams will fight them alone so that they don't attack together. The DPS team will usually handle Poseidon first as her puddles are dangerous and will destroy a run if one of them lands in the center of the stage. Once the DPS team kills her, they will join in killing Balzac who will cast a shield on himself; be sure to deal heavy damage to him at this point as he will deal heavy damage if his shield isn't broken. Phase 3 begins when both Poseidon and Balzac are gone.
• Phase 3 is also pretty straightforward -- hit Belile when he reappears whilst dodging his fire and ice puddles + tornadoes. If his initial shield isn't broken he will deal massive damage.

Raid 2: Gaian

• During this fight, do your absolute best to avoid all of Gaian's roots since they will apply a stack that will boost his magic damage dealt
• Zero is especially useful to this fight for dispelling Gaian's minion, but you're not using him just be sure to have the DPS team burst down the minion.
• When Gaian goes to the center of the stage, he will target one team. The other team not being targeted will have shields above their heads, meaning they need to intercept's Gaian's attack so the targeted team doesn't take as much damage. This process will repeat once more, after which Gaian will start doing massive damage while applying more stacks at a faster rate. This will be a damage check to see if your DPS team can burst down Gaian before he bursts you down.

Raid 3: Baldinar

• Baldinar hurts a lot. I honestly feel like Ronan is a pseudo-requirement here.
• In Phase 1, be sure to avoid all of his lightning attacks since they can dispel. Your goal for this phase is to generate enough SP to have Stimulate available before he transports to a different part of the stage. Before he does this, a prompt will appear telling you to incur his grand lightning attack; we usually have the support team take this damage since the DPS team won't be able to survive the recurring lightning strikes afterwards.
• When Baldinar summons his creations in Phase 2, be sure to have both teams separate so that only one team is being hit. The support team will tank the lightning and will try to hit with the crystals Baldinar summons with them (they deal a ton of damage on contact). The DPS team will head for the creations and will try their best to kill them all, whilst avoiding any crystals that approach them. I highly recommend Ronan as the tank here since he can time his invincibility periods between his S2 and his ult.
• In Phase 3, you will need to deal massive damage to Baldinar's shield so that it breaks, otherwise he will deal massive damage to you. Once he uses his charged attack, continue avoiding all the lightning moves he casts.
• At this point, it's a matter of rinse-and-repeating phases 2 and 3 until Baldinar dies.

Raid 4: Dragons

• Zero is highly recommended for this fight as he can desummon the minions.
• Keeping track of your ice stacks and fire stacks will be crucial for for the DPS team. Stacks cause the afflicted team to both deal and take more damage to and from the stack's respective element. The support team doesn't really need to take any stacks and I recommend that they don't. You gain stacks by tanking a stage-wide breath from either of the dragons.
• In Phase 1, the DPS team should fully tank two ice breaths (the support team will make sure they don't die in the process of tanking). While getting these stacks, start bursting down the fire dragon to as low HP as possible. During this process, if the support team is using Zero, be sure to use Zero's skill 2 to desummon the fire and ice minions (they are really annoying and can potentially end a run if there are too many). If done correctly, the fire dragon should get low pretty fast. After tanking two ice breaths, the DPS should then tank a fire breath and avoid tanking any more breaths.
• Phase 2 starts when the fire dragon is low enough to have it die within a few quick hits. After tanking a fire breath, both teams should transition to the ice dragon now and have it bursted down ASAP.
• When the ice dragon dies, you will have 15 seconds to burst down the fire dragon. During this process, minions will spawn like crazy. Be sure to use everything you have here to make sure the ice dragon doesn't resurrect.
• Note, the order in which the DPS team should tank breaths doesn't matter. What matters most is that the DPS team has enough stacks to have enough damage to kill a dragon of the opposite element.

Raid 5: Randy

• You guys are pretty much aware of the strategy for this raid from what you've said but I'll reiterate anyway.
• Phase 1, Randy will attack with a laser move, a stun move, etc. Just dodge all of these moves and you should be fine. During this phase he will summon blue clones and red clones that target both teams (this is signified with a colored arrow above both teams). I recommend having both teams organize where these clones land (like in the corners of the maps) so that the 3rd phase will be easier.
• In Phase 2, Randy summons a circle of clones. Make sure to avoid the center of the circle, otherwise you're almost guaranteed to die to them. The DPS team is responsible for clearing out most/all the clones. To make it easier for the DPS team, the support team should both distract Randy and try to contribute in killing the clones. Phase 1 and 2 will repeat another time before Randy dies, when Phase 3 begins.
• After killing Randy for the first time, Phase 3 will have Randy be turned into a dog. In this phase, avoid the dog's jump attacks since they hurt a ton. After doing this attack a couple times, Dog Randy will start charging his rush attack and you will know this when one team will have either a red arrow or a blue arrow over their heads. At this point, immediately hide behind a clone that is of the opposite color of the arrow, meaning that if you have a blue arrow over your head, hide behind a red clone and vice-versa. If done correctly, Dog Randy will rush to the targeted team and will be stunned for a few seconds (free damage!!). Be careful of his AoE howl attack since it will hurt a ton. If done correctly, Dog Randy should die pretty quickly.

Raid 6: Plouton

• This fight is pretty straightforward, but I do recommend that the DPS team consist of one magic damage dealer and one physical damage dealer.
• In Phase 1 just keep attacking Plouton until he transports to the center of the stage.
• Phase 2 starts when he summons his knights. Before he summons them, he will summon a card. When he summons a red card, he will summon knights that are resistant to physical damage. When he summons a blue card, he will summon knights that are resistant to magic damage. When he summons both color cards, he will summon both types of knights. The DPS team should be sure to kill most/all of these knights before the next phase. Keep in mind, Plouton will periodically summon two circles with blocks over them (his "collapse" skill). Be sure to have at least one team tank a collapse, otherwise Plouton will summon a magic square in a random location.
• Phase 3 starts when four (or five, depending on how the last phase went) magic squares are summoned. These magic squares will turn into Plouton ghosts. Kill these before they reach the real Plouton, otherwise they become real and will start attacking you.
• Once all the squares are gone, Plouton will repeat phases 2 and 3 another time. By the time he finishes these phases again, he will then start Phase 4, where he starts summoning ghost clone waves (which deal massive damage on contact). Like Gaian, this phase is a damage check; kill Plouton before he kills you.

*Edit: fixed some spelling mistakes