Working as IT without a degree

It's probably not very likely.  A question you should ask yourself is, why should an employer hire you over another candidate which has a degree AND certifications?  There are many candidates already in Germany and the EU which may be better qualified.

As Romaniac said above, to have a chance you need to find an employer willing to hire you for a job that requires your special niche skills and for which they cannot find any suitable EU citizen candidate. Nothing in life is impossible, but it's your decision after which of your dreams you chase. Good luck!

The next problem will pop up at immigration. If you don't have a diploma you're Mr. / Ms. / Mrs. Nobody. BTW: A D Visa is not the work permit to work AND live here!