Well, having reloaded my game...I was able to beat the Draginol, but only through extreme measures. After they had sprung up on one of my systems, they took over another major system before I made peace with them by giving them 2 more. So they then went on to attack the Altarians and the Torians, obliterating their fleets. THe odd thing was that they conquered 4 more Altarian worlds, but stopped conquering any planets after that, as if they were out of transports. But their overlords were swarming the galaxy.
So, I devised a drastic plan mentioned above. I put all my ship building efforts into constructors and spent years building 8 terror stars. The Draginol must have been too busy dealing with the other civs, because they didn't seem to notice me building and then moving them inch by inch to the borders of their territory. Once they were all complete, I moved them into Draginol space, right next to the planets. The order was given...
And the $@%&!*# senate overruled me! Stupid fools, I was trying to save the galaxy from unparalleled evil! So I went to the Torians, asked for an Alliance...got it! And a turn later, I went to war with the Draginol. However, this unfortunately caused them to unload all their ships from their worlds (how they are allowed to do this when it isn't their turn, I don't know).
But it was too late for them. I had all 8 terror stars fire at once...and obliterated all 8 Draginol systems. Billions of those bastards were vaporized, along with dozens of planets, including the original Altarian homeworld, which had over 100 billion in it alone. The next turn, the Draginol ships made their last dying gasp, destroying every terror star...but then they vanished. They are gone.
And I am left to weep at the unparalleled destruction. 8 suns obliterated...
Well, the rest of the game will be a pushover for me, as the Torians are down to one world (thanks to the Independent League), and the other civs are already gone...