Originally Posted by
Unregistered
One element to take into account is that for each fight against a boss for which you don't drop a girl, the drop rate is incremented. And that increment is function of the boss you fight. Dark Lord increments more than Silvanus.
So, yes, a mix of bad luck and lower increment rate can realisticly explains why you didn't drop yet.
For what it's worth, someone on discord dropped 3 boss girls in same day last monday (without using kobans). So, yes, it drops. But as with everything RNG based, it might be very quick or take some time.