Vibrate has been hit or miss for me for several months, too. I'm running the 8.1 preview, but I've had vibration issues since before I upgraded... sometimes notifications and calls will react normally with the correct vibration (short-long, short-long, pause, repeat for calls; single/double/triple vibration for various notifications). Sometimes notifications will trigger a vibration that will be cut short, and sometimes the phone will not vibrate at all. This all happens sporadically without ever changing the settings.
Sometimes I've been able to get vibration back on track with a reset, or with a full charge, but recently it's just not working at all. I had the phone in my hand just a few minutes ago and my wife called, and there was absolutely no vibration. I've gone through this thread and checked the Touch settings as instructed, even toggling them and restarting twice. I guess we'll see what happens.