You don't like playing games online - but most people do. (I'm not big on online gaming, personally - none of my RL friends have consoles. But online gaming is a necessity these days, and it's fantastic fun playing with strangers on games like COD, FIFA, and L4D...)
It's completely ridiculous that a premium FPS game in 2012 doesn't have online multiplayer.
Having local multiplayer and a couple of online gimmicks doesn't help. Quite the opposite - both factors just emphasise the fact that the developers know the game should have online multiplayer, and the engine is capable of it.
Not sure how the online zombiefied friends thing works, but from what you've posted there it sounds like it's open to abuse, with people able to gift weapons etc. to friends to give them a head start, by suiciding... There's probably more to it than that, and hopefully such abuse isn't possible, but tbh I don't really care one way or the other, because it's a massively flawed game(#1) on a massively flawed platform(#2).
As for the length of the single player campaign, why would they chop 10 hours from the campaign if they added online multiplayer?!
"Look chaps, we've just about finished making our game but the online feature still isn't working right. We can get local multiplayer working fine, we just can't get the online version to work because Nintendo's online infrastructure is so shite.
I feel bloody aggrieved about that, but we'll give the punters some silly gimmicks instead. You know - online leaderboards, their reanimated corpses pop up on each others' consoles, that sort of thing..."
"Boss, boss - we've finally figured out how to get online multiplayer to work. Turns out Nintendo's online infrastructure is workable afterall - we'd just put a zero in the code where there should've been a one!"
"Fantastic news, lads. Start hacking the story to pieces - I want you to dump two third of the story and locations so that we can add online multiplayer."
(#1) No online multiplayer = massive flaw.
(#2) "Asymetrical gaming" console = massive flaw.