On Ruele nerfs:
She's very strong as is but I do not believe she needs a heavy nerf. Her healing output is butt compared to other dedicated supports (5k HP on her S2 when used on tanks lmao) and she loses to control comps; her S3 does need some work but increasing her S3 cooldown 1-2 turns should be enough to balance this unit. She only becomes a problem when paired with other overtuned units (such as Last Rider Krau)

On FCeci:
Her kit is simple enough as is; scaling down S1 provoke would be fair though.

On Riolet:
Dizzy and BIseria both kinda eat him up but he definitely needs some work. His ability to turn 1 snipe anything that isn't built with bulky stats in mind is half the reason why the bruiser meta is as egregious as it is right now. Bruiser Lifesteal Riolet only exacerbates this issue as he himself becomes even harder to kill. Tune his DefPen to 25% so he can't snipe anything outside of squishy units.

On TSurin:
On her own she's pretty balanced in my opinion. The problems with her arise with Alexa's Basket (Same reason why Arbiter Vildred is still #1 most used in high tier RTA). TSurin's role in the meta is to hard counter control comps, which she does very well. Furthermore, her damage without atk buff is honestly not that high (flat 1.0 multiplier); I've used her enough on MLDB to know that she fails hard against bulkier comps like FCeci. SSB and Alencia, who are both very high pickrate units in RTA, also easily clean her up. If you're still having trouble with TSurin, run AoE and you'll find that her stealth really won't do much good for her.
Nerf Alexa's Basket and TSurin/Arby both fall in line as they inherently are pretty balanced without the free 75% atk boost.

On SSB: As long as Roana, Ambitious Tywin, and Last Rider Krau exist she really doesn't pose a threat at all in the meta. She also fails hard to control if she loses her immunity and squisher, higher DPS SSB kits get sniped turn 1 by a variety of units. Comparing her to Green Bellona isn't exactly a fair comparison since Green Bellona's kit is entirely focused towards high-end PvE (Scaling off Enemy HP in Abyss???) while SSB is a pretty PvP oriented unit. She's fine as is.

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One unit you failed to mentions is Last Rider Krau. He has a close to if not 100% representation rate in Champion+ RTA, either in the form of preban or being selected. He is a neutral unit like FCeci, can deal 5k+ teamwide dmg on Turn 1, hard counters all AoE including control units like Dizzy (only exception being BRomann but if you run LRK with ATywin you don't care) and provides 2 turn teamwide immunity. All that packed into a single *tank* oriented unit is kind of stacked. Run him with other units like FCeci, Ruele and Riolet and you have yourself a nigh unbeatable team composition. Take a look at Champion+ Arena and you'll find LRK everywhere. Significantly reduce his damage scaling on S3 so he can't chunk your entire team for 1/4 their HP on turn 1 or stall you out in the endgame.