My opinion, it'd be either a 0SP 1/rest clicky (possibly expandable via enhancements), OR a (insert normal SP cost for the level) unlimited usage clicky.
You could argue that with no +40% damage enhancements and no +crit enhancements it's subpar, but on the flipside you'll see clerics stacking BB and WoF and just kiting through both at once.
/shrug.
I'd like to see domains, but they'd probably prove harder to balance than to implement. (That's also my opinion on why there are nor sorcerer PrEs yet.)