Thats originally why I had pecil in my party was for shellga, but now I use a shared sb heavy armor that casts shell start the battle with a soul break and I swap in banishing strike/saints cross when needed. I use red xiii for lunatic high for hastega/protect. So you think I should swap Pecil for Ramza for 2nd support (and I have his curaga sb if that accounts for anything)(oh also just got Setzer's cards maybe make him my 2nd support?, would the attack and magic debuff stack with all my other debuffs since its attack and magic?) and flex Celes in for Cloud or Rinoa depending on what I want?
Really got too many soul breaks to list them all probably, been playing for awhile, just very casually mostly collecting loot.
It sounds like you have a good collection of major soulbreaks:
Celes BSB (ATK/MAG stacking buf
Ramza Grand Armor (40% heal + Protectga)
Relm Curaga + Regen SSB
Setzer ATK/MAG stacking break
Cloud SSB
That's a good cast of characters. Setzer doesn't have the best stats, but he can use swords which is far better than most supports. Use Setzer for two Breakdowns with Battleforged, Ramza for Full Break and Lifesiphon (charge up that Medica!) with Battleforged, Celes for hitting Weakness or Saint's Cross duty (hurray +20% holy dmg sword!) with Mako Might, Cloud with Lifesiphon and whatever with a +DMG RM, Relm with Curaja + Shellga with doublecast heal RM. RW should be Shout.
This group easily defeats all single-target bosses without breaking a sweat with very little S/L needed ever - two great heals, 2x Breakdowns + Full Break + Setzer's stacking debuff, Protectga (Ramza's SB) and Shellga built in, and Shout/Celes for huge stacking ATK boosts that laugh at needing Realm Synergy because you're hitting the soft cap regardless. This team is also set up for the future as Ramza, Cloud, and Celes all getting to 99 early on.
Cloud is your first character to replace - his SSB isn't that good, his skillset is subpar, and his equipment selection leaves a lot to be desired. Setzer's stacking debuff comes in handy, but replacing him with a more valuable character down the line is another thing I'd look for (Vaan and even Agrias are the two best direct replacements).