Compare it to Prayer, which buffs and debuffs everything you do except ability checks (which are rare unless you count initiative) and also weapon damage. It is only +1 though, while this is up to +4. This also lasts minute/level instead of round/level, which honestly is about one battle per spell either way. The emanation is smaller than Prayer by 10', but it's still enough.

I would put it at about Cleric 4, but the +4 sacred bonus to lots of stuff is quite nice. I might cap the bonus or penalty at 3 instead... but the diamond dust probably means 4 is fine.