The E3 has basically the same requirements as the H1B (regular work visa), the main difference is that there is no cap (whereas H1Bs are capped and it's basically a lottery whether you get one or not).
IIRC there is some way to avoid the degree requirement if you have a skilled job and an equivalent # of years work experience.
Technically E3 has a cap, but since only Australians can apply for it (as opposed to the whole world applying for H1-Bs) the cap has never been reached.
I really doubt it matters. F1 student visa isn't dual intent either, but a lot of foreign students end up marrying US citizens and adjusting to green cards in the US.
IIRC there is some way to avoid the degree requirement if you have a skilled job and an equivalent # of years work experience.