I haven't had any such experience of that, so this post is simply my thoughts upon reading the thread.
If the - dirty rushing - sororities are national, and the greek advisor doesn't seem to care, perhaps having a word with the other national sorority offices may be an idea? I mean that in the context of a national forum about X campus; dialogue between the national offices of those sororities. It would be in their interest to interact with you and LISTEN to discuss a campus where their sorority (and of course 'yours') is experiencing dirty rushing (otherwise NPC may take a somewhat dim view
).
In the event that the national sorority is in fact one with one of the 'problem' chapters installed, diplomacy would need to be exercised so you could take more of an 'aware there are problems with such and such issue at X campus, problem is endemic, difficult to determine which sororities are involved, so attempting to have dialog for the continued success of all our respective groups' etc approach (rather than say there's a problem and you guys are causing it). NPC may offer further solutions/advice?
If they were regional and so without national offices, the founding alumni responsible for them, for example, might be none too impressed to hear what was going on.
If local... they are somewhat less accountable to others. In that situation meeting with the greek advisors to try and stress the gravity of the situation - eventual erosion of relations between chapters, little inter-greek spirit on campus etc, and how it is in the college's (and therefore the advisor's) interest to make sure inter-greek life does not end up in a huge mess on their watch, may help arrest the decline of proper procedures.
Good Luck
.
- Richard