'normal' couples can use it
Charming.
As half of an 'abnormal' couple I'll try to shed a bit of light on this for you.
It sounds to me as though what you are really needing to do is apply for a spouse visa as you appear to be wanting to rely on the relationship as the basis for the application.
The two visas are essentially the same, the interdependency visa being introduced as a couple needs to be of the opposite sex to be able to apply for the spouse visa.
The problem that you are presented with is the 12 month relationship requirement. See
http://www.immi.gov.au/migration/fam...lationship.htm and
http://www.immi.gov.au/facts/35relationship.htm
It seems clear that you would probably not fulfill the 12 month requirement and you would probably not be eligible to have the requirement waived.
If you have not been living together for 12 months I think that you would have to come up with some pretty compelling evidence to pull it off. Joint finances will help, but appears as though you won't have that sort of evidence.
An agent may be of assistance, but they are expensive. If I were you I would probably gather absolutely everything you can to assist you and then lodge the application yourself - it's not a difficult process.
Good luck.