Is alarm vibration suddenly broken in iOS 7?
(Sorry making this an answer, I don't have enough points to comment yet)

This probably isn't your issue as you've recreated your alarms, but I can cause my phone (iPhone 4S, 7.0.3) to do only "one" vibration by creating conflicting alarms for the same time, one having the sound as "none" and the other to any random sound.

It took a bit of juggling, but I managed to have the sound alarm start first and then immediately the none alarm started and the sound and vibrations stopped.