Yeah it did kill his combo game, somewhat. I said that the nerf killed his long combo strings and the ability to combo at very low percents. Also, like I said in a previous post, he lost a lot of aerial combo options that he had before nerf, and in return he got....nothing. The extremely low base knockback and high knockback scaling works against him because his greatest combo tools are his aerials. In other words, he cannot just chain long aerial strings into regrabs and such because the low base knockback allows people to escape fair easier at low percents or just DI down and shield or roll away for fast fallers.
Also, how does the nerf help people "play better" in the neutral? Just blindly going for grab to get the "cheese" is always a bad idea, and people got punished for using Luigi that way pre-nerf. Luigi needed his cheese because his gameplan is relatively simple and his cheese allowed him to go against top tiers in the game.
Like I and G.Stache said, Luigi still has favorable matchups with lower tiers and most mid tiers, but he just cannot compete against top tiers because the nerf took away many of his most valuable tools (very long combo strings at low percents, and a viable kill setup), which explains his tier placement in the 4BR tier list (top of the mid tiers). It was not my intention to make it sound like Luigi is duck hunt bad, since Luigi has excellent CQC options, still a good damage racking game compared to some of the characters in the roster, and his relatively simple gameplan allows Luigi players to adapt and respond more quickly to player habits and playstyles.
Well, I kinda also showed that Luigi goes even or beats a majority of the high tiers. It's the big three (Rosa, ZSS, and Sheik) that shut him out from a high tier position. Having a bad MU against Mega Man, Toon Link, and debatably Pac Man/Samus would be fine, it's just that a Luigi needs to know how to handle ZSS, Sheik, and Rosa very well to have the best possible odds. And even then, it's still around -1 against those three when played super optimally (AKA, what I like to call the Lame-eegi way)
Should also be said that even though Luigi's d throw was nerfed, he is still probably around top 3, if not the best, at damage racking. Seriously, his d throw is still superb. And that's not the only this to look out for. Jab, falling Nair, U throw (on fast fallers), and d tilt trips are all good at getting strings going. D throw was never the only option, and I doubt everybody knows how to DI all of these since you saw the best Luigi's only using d throw for the most part. Not to mention the good damage output from Luigi. Something characters like Mario and Sheik probably wish they had more of.
IMO, Luigi is still arguably solo viable, and definitely an amazing counter pick option if you just put a bit more time into him than what you previously had to. I don't have a fully fledged tier list of Smash 4 (too many patches and new characters) but I'd probably still have Luigi sitting around the top 15 area. That being said, the Luigi playerbase seems to be split into two 'factions'. The Luigi optimists, and the Luigi pessimists. I'm probably considered rabidly optimistic. I'll even admit it outright; I'm a bit biased when it comes to Luigi. But I'm not saying that Luigi is downright amazing, he lost a very potent tool from the nerf and he's always has had clear cut weaknesses. But I don't think he's very far away viability-wise from some of the high tiers like Mario and Pika (assuming you think Mario and Pika are both around the bottom of top 10 like I do).
Also, is it just me, or does this debate sound like a lot of the kind of discussion we would have 4 months ago when the patch just came out? Man, this thread loves going through circles. Anyways, Luigi does have a few problems, but he's far from a bad character. Top mid tier is hardly a bad place to be in Smash 4.