I don't recall him ever lasting long (by himself) in hand to hand against anyone super-strong other than Cap, who was too nostalgic to really go after him. His fight against Black Panther was blink and you miss it with Bucky mostly just trying to run away and Iron Man tossed him around like a rag doll (yes, he survived, but so have plenty of other people Iron Man fought). Don't recall specifically how 'massive' any of his falls were, but surviving ridiculous falls is a fairly common trait even in supposedly human characters so it doesn't mean much to me unless it's really explicitly called out as truly extraordinary (like the scene where Cap jumps with no parachute). (Hell, the biggest fall I can think of that Bucky survived would be the very first one from the train - the one that happened when he very clearly and definitively had not yet been enhanced.)
I will agree 'normal human' was the wrong phrase to use. Obviously he must be enhanced to some degree. He is faster and stronger than characters like Widow, Hawkeye, Falcon, etc, and if he weren't enhanced somehow, he'd be dead/dying of old age by now, anyway. But I've never seen any reason to believe his enhancement was anywhere near the level of Cap's and his fighting prowess - at least outside of fighting normal humans - is pretty much all about the arm.
Maybe Hulk level is overestimating him. It's hard to say exactly what level it is, but considering how effortlessly he rips through prisons, tosses dozens of trained soldiers around simultaneously like a child playing with toys and literally lifts a guy who clearly weighs several hundred pounds at least with just two 'fingers', I don't think there's any doubt that he's dozens if not hundreds of orders of magnitude stronger than Bucky and certainly Sam.
Also, whether Mr. Fantastic/Ms. Marvel exist yet in the MCU or not is completely irrelevant. I'm just using their names as a shorthand to convey a certain kind of ability that Groot clearly possesses - an ability which means, among other things, that it would be almost impossible for Bucky to stay out of Groot's reach. And also that any damage Bucky could do to Groot would be temporary at best.
He doesn't need any. He's not a flyer. But I look back at the camp fight scene in Guardians two, and I don't see any hope in hell of a guy like Falcon actually getting a lock on that level of speed and evasion. But vice versa - I have no problem believing Rocket can come up with something that can track Falcon.
And the Nova Corps. And I don't automatically accept the idea that the Ravagers and Sakarans are just total pushovers that offer no proof of capability. Especially not when we're talking here about Sam and Bucky. Not Steve. Not Stark. Not Natasha. Not Fury. Like I said, they're great soldiers. But they're dependent on what they have to start with - they have zero potential for pulling some unknown ace out of their sleeve and their tactical successes are almost exclusively as followers and/or hidden assets with the element of surprise.
One of the interesting things about human observation is that it's unique to each individual - I've seen 5 witnesses to the same event give different evidence in court.
What I'm saying is that you are taking away some very different information from Bucky's feats - if you have indeed seen "Captain America the Winter Solider " and "Civil War" - Bucky is completely uninjured from at least a 100 foot fall onto a neighbouring rooftop, and yes he rolls at the end, but if a real human did that, their ankle bones would be coming out their ears. He also jumps off a building, onto the street to escape Black Panther - and then runs away, outpacing a bunch of cars.
Having seen Bucky and Cap fight, fall and run, they are roughly equivalent - with Bucky's metal arm being even more durable (bulletproof) and capable of smashing concrete.
In Winter Solider - Cap jumps onto the helicarrier, at least 100 feet below and rolls out of it - that just ain't possible. He gets blasted off the bridge, smashes into a bus losing his shield in the process, which then crashes and gets up a few seconds later, unscathed.
I could take the time to list all the falls Bucky has taken - or point out that yes people have survived punches from Iron Man.....people like Thor ! And as for Bucky's fighting prowess, you clearly went away from his fight scene with Cap on the main street ( before Cap knows who he is) with a very different impression than me.
You might read some articles which describe just how strong Captain America has to be to pull off the feats he does in his films - e.g. in Civil War he lifts a guy by his ankle and slams him into a pillar - in Age of Ultron he goes toe to toe with Ultron and throws a motorcycle with enough force to smash a large jeep, while riding it, which means he also has to redirect the forward momentum of the bike. And of course he holds down a helicopter that's trying to lift off without being ripped apart.
What's Groot's big strength feat again ? Lifting a guy by putting something up his nose - believe it or not, if someone shoves something up your nose, you'll become very compliant and easy to move - I saw a Policewoman do this with a very large drunk and a ball-point pen.
As for ripping through prisons ? During the escape from the Kyln he tears off the cover of the
box that holds the battery Rocket needed, otherwise he smashes a few drones, throws a Nova
Corps guy off the guard tower, and that's about it. Most of the drones get taken out by Rocket
once Drax chucks him a gun - again both Drax and Gamora were able to easily break free
and tear right through Groot's tendrils. I think you are drastically overestimating Groot's strength and durability - and he's unlikely to be very durable against fire, given that he's made of wood.
You cannot compare MCU Groot to comic book Mr Fantastic or Ms Marvel - I put to you that MCU versions of characters are quite different to their comic book counterparts. You can't compare them because you simply don't know how stretchy an MCU Ms Marvel or Mr Fantastic would be. You could compare Groot to the FF movies' Mr Fantastic, but he's easily much more pliable and stretchy.
Rocket's evasion against the Ravagers on Berhart worked because he used the cover of the trees to his advantage, it was dark, and he took them by surprise. How did he do against Nebula's blaster ? I think it's unlikely that he's bulletproof, so all Sam or Bucky need to do is bust a cap in his furry ass.
I will say that if Rocket knew exactly who he was fighting and had a bunch of prep time and gadgets he's got a chance. Although none of that made a difference against the Ravagers in the end. He and Groot were still taken prisoner. Groot and Rocket's best feats are still against no name goons, while Bucky's best feats are against Cap, the best fighter in the MCU. Sam's feats are not so impressive, but at least against Crossbones' elite mercenaries rather than just Ronan's cannon fodder. Sam does have some feats against Iron Man and War Machine, during the airport fight in Civil War, but he doesn;t come close to taking them out.
In the end, I'm not saying that Rocket and Groot could never beat Sam and Bucky, but Rocket would need significant prep time and better gadgets than he used against the Ravagers. In a straight up fight, if Bucky and Sam have weapons they're going to wipe out Rocket and Groot.
However, regardless of what you or I think, the votes will settle this.Cheers,
Vision wins 3-0. 
