If you're getting swarmed by dreadnoughts, you're taking a really long time to spread out.  I only saw them one at a time.

I just played through, first time.  The last mission was a cake walk.  You have enough resources in your corner area to support multiple cruiser production, and you have an anti-dread cruiser to work with as PHC, killing them is really easy.  I was able to save Mac with about 50 logistics in mostly cruisers while I pushed left with a similar force around the time my first dread was coming online.  It took Athena that long to take out the starting frigates.  By the time I had to rescue him again, I could send him three Cronus fleets while I massed even more forces to take the lower left.