I disagree with all your points except the one about joining the losing match. I do despise that.
I find quickscoping to be more of a skill. I've tried it and I did 5-12. I in no way helped my team and was no way overpowered. I remember in MW2 you could do knifing classes, and do 20-5 on your first try. THAT was OP. Quickscoping is just a talent of the user and you can't claim that that is OP.
Nube tubes are weaker now. In fact, I think ALL explosives are weaker now. The maps are a a lot smaller and you're more vulnerable but I think in my 10 hours+ of multiplayer, I have died maybe 4 times to nube tubes. Grenades, I think they're weaker now too, I don't get killed by and rarely kill with grenades. They can work well when you use them right, but random grenades just don't work anymore. You don't even have time to cook them, so you can't even get an early grenade off.
Akimbo weapons get defeated from a distance. Yes, I said the maps were smaller and faster, but they do have long lines of sight, and they need to have steady aim to make use of that. That takes up their Perk slot, they'll probably miss Sitrep, or more likely, dead silence (unless they run a specialist streak).
Assassin Pro so far seems pretty OP, but I've been finding people haven't been running it as often. If you go with a Support Streak, you will probably run Assassin Pro, but if you go with an Assault Class, you probably want Hardline Pro, so that you have a better chance of getting your streaks. I find all in all, there is a lot of balance in the game. Besides Assassin Pro, all the weapons seem balanced, maps, and pretty much the whole set up. MW2 was a mess in terms of balance, and it was never patched. Black Ops started unbalanced, but was patched frequently. Still, Ghost Pro was rampant and you could NEVER call in aerial support since every had anti-air as their secondary (since all the secondary weapons sucked).
I find there's like 80% new killstreaks, perks have maybe 25% of them new but they're more balanced. Overall, the multiplayer is solid. If anything, the maps lend themselves against sniping, so sniping is underpowered if anything.
As for story mode, I liked it. The game is about the start of a fictional world war three, did you expect it to be realistic? Why not make it big? I felt like I was in an action movie, it was super over the top, but it was exciting and awesome. The story line wasn't as good as the first and second, but this was meant to be the end of the war, not really the plot-twisting start of it like MW and MW2 were.