I ran this title for my first try with the onager.

I think there are two benefits to this card.

1) allows a turn 1 shot at ignition long with the particle cannon, as long as you have hondo or tarkin?

2) allows you a second go to reposition the aim point in case, since the end of the onagers turn, the target has changed position.

Is this right? Any other benefits of cataclysm?

Im thinking next to give rachell a go with romodi, and park behind a big fat asteroid field all game...

Yes, shooting in Round 1 (and maybe increase your range more with Officer Ozzel) and reposition your ignition in case a Raddus comes out or a fast ship is out of black/blue range.