G&W's moves don't really lead into each other very well (contrary to how I may have been making it look), he's not very fast (not slow either but not fast), his only projectile is pretty bad, and he doesn't deal particularly well with people being right up in his face. He also basically only has one approach move on most stages (turtle), and that forces some cleverness since he totally falls apart if he can't approach. A random thing that sucks about him is that his tech roll is the second worst in the game (Charizard has the worst), though his normal roll is below average as well (still usable). His grab is really quite bad as it's both a bit sluggish and has pretty poor range, and he has the single worst pummel in the game, bad to the point that he should basically never use it against opponents who break grabs correctly except at extremely high damage. His throws really aren't too bad, but he is burdened with three basically functionally identical throws (u/f/b) that leave him unable to kill off walk-offs effectively or position opponents anywhere but up with his throws in general and the fact that many opponents basically always tech the dthrow, greatly reducing its usefulness (still good, but not nearly as good as it seems at first). Basically his whole strategy is to zone with his good long range moves (bair, dtilt) and try to sneak in his very powerful smashes and fair whenever he can (though he pretty much always has to land them "cold"). He has a few other nice things like the extra mobility options that Fire and dair give him, but, while he is indeed a solid character, he's far from invincible.
G&W may look spammy, but there's some serious business spacing going on there. You also weren't applying SDI against the turtle or teching the dthrow which made things a lot easier on me... In general I've accumulated a lot of little tricks and traps with G&W (he is not only my main but the only character I use seriously, and even factoring in the countless hours I've spent with every character thanks to this project, I still have used G&W more than everyone else put together), and you kinda kept falling into them (like that dair on the platform against Bowser thing, which you should have responded to by baiting the dair and punishing the landing lag with either fair or Flying Slam), and I wasn't really giving you room to think out what I was doing a lot of times since I'd run up and smash you or turtle you all of a sudden after doing stuff like that. What I'm trying to say is that G&W seems like this because I was really slamming you with everything he had, and when G&W is doing well, he is pretty overwhelming. I don't think he's really imbalanced at this point; he seems to generally settle into the normal kind of good.
Also, bucket braking is nice, but it doesn't really enhance his survival that much while simultaneously giving him more work to have to do quickly upon being hit. Actually being heavier would definitely be more useful; any "survival of a middleweight" is really more attributable to his excellent recovery than Bucket Braking (that just puts him dying later than guys like Squirtle and Meta Knight). I'm just really used to what it means to be light, and as a player, I'm pretty good at survival in general (positioning and avoiding certain types of threats, combined with good DI, really increase your survival with any character).
In any case, good games.