Hello there!

Were you sure that were really empty domains? Have you checked whether had history of any kind with web.archive.org?

What i'm understanding from your question is that the rankings were hurt just when the redirection impacted and indexed.
Solution? do not redirect those domains to that kw. Just make a 301 to the home, root domain to root domain:
empty-domain.com->main-domain.com

Also, have you checked for any other reason for that drop in rankings? Bad backlinks, an increase in your competitors authority, bad own optimization or better competitors's optimization, or any other?

Best luck.
GR.

Hi Kris,

This brings a bigger question: Why do you need a 20 point increase ?

You MUST know that having higher metrics will not make you rank higher. It will increase the chances of ranking higher and impress your clients/supervisors.
In my opinion, you should not focus in metrics, such as PA or DA. Focus in doing what google wants.

To answer your questions, just get (somehow) links with higher PA/DA than your page and make your link profile to have more and more of those links. Timeline? a few per week for the entire life.
Remember, moz's metrics look at the most, the backlinks pointing to your page and the links in the pages related to the backlink and you website... So the key in Moz' s metrics: BACKLINKS!

Hope I've helped.
GR.

Hello Jaro,

What Andy says is right, im backing him up. Remember to not include that URL in the sitemap.

Also is a good moment to say that with the robots.txt you just tell google bot not no follow it, that differs from indexing it. There are cases where URLs are indexed instead of being "blocked" in the robots.txt.

The fine way stop google from indexing a certain URL would be adding the meta robots tag including a noindex atribute.
Here there a quote from the Webmaster central help forum in Google:

If you block a file from crawling and Google discovers a URL for that file on another site, it may still index the file using whatever information it can find, even though crawling is blocked. So robots.txt disallow does not necessarily stop something being indexed.
(in the ets answer, a note below the Disallow part)

Hope it's clarifying.
Best luck.
GR.