Getting married may speed up things a bit for you as there may less scrutiny of support evidence and if you did it quite soon, like as soon as you can organise it, there being a minimum months notice needed with a Notice of Intent to Marry, you might shave a couple of weeks off by putting in your application as soon as married given I assume that you were lucky enough to get a 12 months tourist visa without a No Further Stay condition on it.
Have you closely read your visa conditions for even without the No Further Stay condition, it does seem that people are getting 12 months multiple entry visas which are in fact more or less like the ETA where they are only valid for three months at a time. If so, and you have not been leaving each three months, you are kind of here illegally.
If it is a full 12 months and without a NFS, the other thing you may need to consider is how were you together prior to you entering or was there some separation period for you need to show you have been together at least 12 months, not just 12 months and certainly not 12 months less a week.
some people do a trip out, see a travel agent who can book an ETA for those not eligible to do it online and return so as they have that additional three months to get over the 12 line.
Getting married will at least remove that hurdle but you need to be quick about it.
