You would have issues getting a different visa than the 457 though, they require 5 years experience if you do PR by yourself.
Does the 457 visa mean that there is no requirement to meet the educational requirements for a Software Engineer on the SOL?
Effectively, my lack of BSc won't stop me if I can get on a 457?
The 457 requires you "have skills, qualifications, experience and an employment background which match those required for the position". I never finished uni and got a 457 in 2008 (I'm Swedish). I did have ~10 years of experience though.
The Department of Immigration have lots of information on their site, http://www.immi.gov.au/.
I'm trying to figure out if they will accept me being sponsored by my employer with my 2.5 - 3 years experience and DipHE... basically, will they take me despite my lack of BSc?