I, honestly, don't know what's happening here. I dunno if you're delegating pulseaudio to jack or viseversa. Anyway, I use this method to enable my http://us.focusrite.com/usb-audio-interfaces/scarlett-18i20 in Fedora 20. I hope it helps out:
Procedure
#!/usr/bin/env bash
pulseaudio -k
pulseaudio -k
pulseaudio -k …