Range is relative to how far the hitbox reaches from the character. If he's extending his own hurtbox into the range of fair, then it has in effect lost range because the point of range is to be able to attack from a distance to avoid danger. Even you mentioned how this can be a nerf when referring to DK's bair later in your post. In addition to that, he leaned forward in the other games too, in fact it seems like he twists his body more on the Z axis in this game.
I think the damage should have been left alone on fair personally. It really shouldn't be delegated to being ONLY a combo move. It used to do it all, and that's what I love about Ness. It had duration, range, defensive properies, comboability, decent speed, and healthy damage. The new fair lost its range, which as a result diminished its ability to be used defensively, and of course a lot of damage too. Duration, comboability, and speed are all still there at least.
Yes, Marth and MK got nerfed, but they're still plenty good, and I can still see them posing a threat to Ness. If you seriously think he's got an easy matchup against those characters now, I would love to see your reason why. You've still got to work to beat them. And to be quite honest, I don't think Ness outright beats Shulk or Ike either, ESPECIALLY now with the buffs they received (and MK). And I forgot to mention Rob and his giant hitboxes. I honestly just don't see any easy A's on Ness' matchup chart so far, and you need that to even contend for being high tier. Please tell me, what matchups do YOU genuinely believe Ness dominates? I'm having trouble finding them.
No one really killed with their throws in Brawl anyways. It's not like it really affected them at all actually. The only ones that I can think of off the top of my head were Olimar's blue bthrow and purple uthrow, and Lucas' dthrow. Lucas is gone and I guess that's a shame for Olimar, but he got the mess nerfed out of him to the point where I feel like Olimar players are just numb now.
Saying that bthrow is the ONLY good kill move in this game is a mass overstatement though. What about Mac's 3 fsmashes? Rosalina sending Luma out and mirroring usmash? Bowsers.... everything? Saying Ness has the only good kill move is just not true. In fact, I wouldn't even label it the BEST kill move out of all the good ones.
In conclusion, I think Ness has slightly above average range, still failing to compare to Ike, Shulk, and Rob.
Still has some reliable kill moves. Bthrow and dair were nerfed, uair was buffed. But that's a 2 for 1 exchange.
Comboability is good but the damage nerf on fair sucks.
And his recovery in undoubtedly better, but they DID remove magnet stalling.
I'm not discrediting everything you're saying, but for almost every thing Ness got buffed, there's a nerf to accompany it. You just have to identify it.
Ness' fair is worse as a defensive option, since his hitbox range has been nerfed, that's right, but it still has range forward, even if he can get hit while doing so. It's not like dk's bair range is 0, he can get hit there, which is obviously worse than not being able to be hit there, but that doesn't mean he got no range there
Ness' fair range hasn't realy been nerfed, his hurtbox just got nerfed, which passively limits the option of abusing that range for retreating fairs ... but it's still a nerf, never said anything else
it is way better in terms of chaining moves and other fairs together though, Ness' fair couldn't realy do that in a reliable way unless the opponent got realy low % in brawl
fair overall is nerfed, but overall still a good move, and you will need to use it diffrently
bthrow is the only good killTHROW in this game, typed that worng once, it is far from being the best killmove
i also never meant to say ness destroyes or even wins all those matchups against marf ike etc., he just won't be destroyed that hard by range anymore, he could still be kinda bad against them, but there will be no marf-like MU like in brawl (part of that was the deathgrab, but this still would've been the worst and a realy bad MU for him if there wouldn't have been that deathgrab in the game)
overall changes to ness :
+
deathgrab removed (biggest plus)
uair buffed by a lot (and it even used to be a good move before)
dthrow buffed (less damage, but you can combo out of it in a reliable way which usually results in a higher damage output than it used to be)
pkt1 buffed (a decent projectile now, not realy sure if it is bad now in 1.0.4, but overall it shoudl still be buffed)
pkt2 buffed in tearms or recover power (you can't just jump above ness to kill him, more range, either slides up walls or gives you a 2. pkt2 if you bounce of the wall, still gimpable though)
pk-fire slightly buffed (fire pillar hitbox is slightly harder to escape, and the first hit has less knockback, so the hits connect better)
all smashes slightly buffed (still only mixups)
grabrange buffed (?) not sure about this one, but kinda seemed so for me
psi magnet range buffed
-
fair different, but nerfed overall
dair is nearly useless
bthrow kills a bit later (vectoring is different or removed in 1.0.4, so it should kill slightly early than in 1.0.3, but it will probadly still kill later, BUT the only good killmove in the game)
there might be slight changes to other stuff, but that should be the important stuff, overall he is buffed by a lot acdtually (even keeping brawl ness and removing only the deathgrab would be a huge buff)
How good he'll be depends on his MUs, and specially his MUs vs top/hightiers, but ness is good in this one, specially after 1.0.4 where a lot of better charakters got nerfed while ness only recieved tiny nerfs
Edit: wow, wall of text xD
Edit 2 : just a disclaimer, everything i wrote here is just my opinion, there is hardly any metagame and i haven't even been able to play the game with a gcc, the metagame will evolve and so will MUs and charakters
those are all just speculations of me saying ness has a lot of potential on paper to become a realy great charakter in this game, if there turns out to be one dominant charakter (like mk in brawl) and ness will have a bad MU against said charakter, then hardly any speculation will help you there
just thought i had to add that