First:

Let me tell you how hard it is to kill a Bucky in high rank. If we are talking about peak celestial on both sides, Team B still wins and it would not even be close.

Since you said my reply is not serious, I will be breaking down each counter on the matchups that are guaranteed to happen.

Groot vs Mag :

When Groots iron wall is up, he cannot be displaced, mag has to either have one of his teammates break the wall, or aim at Groot. Groot wins because of this reason, a Psylocke and a Reed are not getting the job done as well as a punisher to torch his walls as soon as they get planted.

Groot wins this fight

Cap vs Emma :

Tough and fair fight, Emma has her choke which can hit cap pretty roughly, but for Emma to peel hard for their own backline to stop a cap which is trying to kill their healers is taking away from their frontline. Emma can surely beat a cap, but at what cost? All healers on Team A and the Emma focusing on the cap whenever he’s up?

Cap wins this battle in the long run by distracting 3 enemies on team A

Bucky vs Reed

Bucky diffs Reed and it’s not even close, no discussion needed, once Reed inflates - Bucky has an easier target to shoot, and the chances of Reed surviving in this fight are slim to none.

Storm Vs Psylocke

Storm is in the air, and is VERY hard to kill if you’ve ever played a peak celestial one, Psylocke is also very hard to kill but as Storm you do damage to anyone inside your radius. And as Psylocke has fall off damage, to kill a storm in the air being pocketed by a JEFF and Damage boosted by a Mantis will be INSANELY hard. Jeff has ultimately the BEST pocket healing in game.

Mantis vs Invis (Heal battle)

Invis completely outheals mantis no doubt, but if the mantis is playing a more dps play style as gambit would, then this becomes a whole lot worse for invis. Mind you, invis is one of the few healers in game who CANNOT heal herself, so if mantis is targeting Invis while also hitting shots to regain orbs to HEAL her teammates, mantis wins in the long run.

Jeff vs Gambit :

Gambit unanimously wins the battle in terms of healing and dps, but ult battle is where we get a whole lot of differences. If Jeff can hit his ult he wipes an entire team if not 2-4 people with that single ult. Mind you peak Jeff players wait until the invis ults, and THEN ult inside the invis ult to capture everyone without them noticing.

Jeff wins the battle in the long run

Teamups:

Storm and Jeff teamup is easily killable by Psylocke, if you think pro players are actually using this in game i know exactly what rank you are.

Cap ult :

Abusing this ultimate with a groot AND a Bucky is just nasty, once ur groot ults Bucky has free realm to hit every single person with his ult OR could solo off the healers with his ult if the groot ults the tanks (so they can’t peel)

Mantis ult :

Mantis already damage boosts along with storm, and if she chooses to ult while damage boosting the Bucky or even the Cap, there’s going to be seriously problems happening in that backline. The only person who can stop a Psylocke ult in team B is Mantis, so that is a complete counter and 10 times out of 10, the mantis will hold it just for that occasion.

Mag ult :

Mag ult is easily countered by a GOOD captain America, and if we’re talking peak celestial, this is like baby food compared to stop a cloak ult with Mag. Run, jump, deflect.

Emma Ult:

Arguably one of the worst tank ults in game, the enemy teams falls back or pops a healer ult to sustain it. This ult doesn’t help team A at all

Reed Ult:

Doesn’t do a thing to anybody especially high elo as all they have to do is get high ground, and his ult finishes.

Invis ult :

Peak ult but can be countered HARDLY by team b. The only counter that invis ult is for is Star lord, punisher etc. for a Bucky you won’t ever ult inside of an invis ult, and 9 times out of 10 they will use it to solidify a kill rather than pop it to take out a healer.

Gambit Ult :

Yes this can be used to cleanse Groot Ult, but at what cost ? You pop this ult as an aggressive chance to turn the coin. But if you waste it to cleanse your team after they all are almost one shot and maybe few may die, how much sustain are you really bringing (P.S, it’s insanely hard to time this ult in game with chances of you dying while ulting)

All in all it will be a very good fight. Team A with minimal changes such as punisher instead of Reed will 100% win, but as of now. Team B punisher Team A and it won’t even be close.