They made a design decision that Slaanesh should get Feel No Pain, just accept it dude. The main part of Nurgle armies still get Feel No Pain anyway. It might seem stupid but even age-old Death Guard mates of mine don't mind the change at all. Bikes also do not all have power weapons/fists and are not in terminator armour, so its not like you are actually doing the same thing.
I think it is intentional, but it is just silly. I never ran combi-spam terminators myself, but I know a lot of Chaos players definitely did, and being forced to count their combi-weapons as combi-bolters or, worse yet, rip off the arms is bad.
I think what he was referring to was options outside of just daemon weapons. In that sense, we got stuff like the Burning Brand, the Scrolls of Magnus, the Murder Sword, etc. The lack of daemon weapons hurts but we've gotten what would probably be called more interesting and unique options instead. The Black Mace isn't AP2, but it will still force a lot of saves; fleshbane makes it a potent monstrous-creature hunting weapon. Whilst not as good as the old Plaguebearer, in that sense, you aren't restricted to Nurgle with it. Not that I disagree with you, I wish there were more daemon weapons.
I don't really have a problem with the Obliterator changes, it's a nerf by losing Fearless but how often will they realistically run off the table if you are using them properly? They aren't meant to sit back and sit in your back-field, they become exponentially more dangerous the closer they get and that has always been the best use of them. In that sense, if they fail a leadership test, they shouldn't run off the board. And even then, being such a small-model unit, it's rare they will fail one anyway. IMO I weigh it up like this - 5 points cheaper for the loss of Fearless and a point of leadership and using the same weapon in consecutive turns but gained Assault Cannons and for a point more than they used to be they can be T5. Considering what usually kills Obliterators is S8-9 AP2 weaponry, that's a big buff in that sense IMO.
3" is fine for a breathing space usually I think you will find, all you really need to do is have part of the base touching that 3" circle. You should easily be able to get around friendly models like that. The only times I'd be worried are in big combats with 20+ models, but how often do those happen nowadays given that units will almost always be cut down at least partially by shooting? And even then, with the pile in rules, as long as your models weren't really spread out when you charged, again there shouldn't be a massive problem getting to the side or behind them.