In the last game I played, I got two mega events and both were much too easy to survive.
First I got the Plague event, still pretty early in the game, I was still colonizing planets. Because I already had the pre-requisite, I could research the plague cure in about 7 weeks with all my income going to research.
Much further on in the game, I got another mega event, this time an invasion from the Dread Lords. They got one planet in the corner of the map. Two turns later I wiped them out with a single transport.
Some suggestions to make these events a bit more mega...
In case of the plague event, maybe to be able to research the cure, you have to be in possession of one special planet (need some rare resource to be able to manufacture the cure) randomly chosen in the galaxy. Imagine all races going to war to try and get that planet. This would make it a lot more difficult to get the cure in a very short period. If one planet would make it a bit too unbalanced, maybe a few planets scattered around the galaxy, but always less then there are races.
For the Dread Lords invasion, the problem was they only got one planet, and not a single ship. If the Dread Lords decided to try and wipe out the galaxy, wouldn't they bring at least some ships? I suggest giving them a fleet at least comparable in strength to the strongest race around. Maybe not all of them in the first turn, but spread out over a couple of turns (think reinforcements every week or so...) Again this would make it a lot more unlikly that you can 'solve' the event in a short period of time.
Just my ideas, any suggestions or corrections? Please discuss...

Scorpiana