I'm waiting for the option to change my class before i start caring about stats.
What probably needs to happen is that they allow you to buy the RNG drop girls by spending real world $$. So, if you're playing for Free, you take your chances, but if you really want to win, you can speed things up / make things certain by paying. I think this is probably better financial strategy on their part than... I'm not really sure what you would be getting people to pay for right now. Stamina refreshes to level quicker? Just doesn't seem to have the oomph that paying for girls would have.
My prediction is that once more worlds are ready they'll up the drop rate on the first bosses, you only really need 2-3 boss girls to get much more money then you'll ever need