I've ignored the 10% damage bonus the Juju would get if it was fully upgraded, but I am comparing a rare weapon to an exotic, the difference between them should be vast.
I'm using a legendary revolver for PvE after coming to the same conclusion as you, I've not even maxed its damage. It's got buffs for an extra round in the chamber so it can be a 13 shot too. I've heard Thorn (the exotic revolver) isn't even that good at the moment because a) it's only 6 in the chamber and b) the DOT it applies doesn't stack, or at least doesn't proc again until the previous effect has worn off.