Onrush is a great skill and definitely worth the Righty choice (plus it can be extended with MP pots a and Sellion), but I think I'm gonna wait on my Dio in case 3rd job comes out and decides to screw Lefty Dios over. My Dio's a Lefty so I don't want to be stuck with half and half.
As far as Mocking Blade vs. Onrush goes on that list, I'd say Onrush tops Mocking if the extension is used (holding the directional key and/or spamming MP pots during), since Mocking time can be extended to 10 seconds.
Arme 4th "Deep Impact"
Does a lot as well, but my screen always lags when I fire it off so I can't tell if it's better or worse than Big Bomb. ><
I miss Lire 2nd's Harpy in this sort of conversation. ._.
And also, As far as power goes, I know it's the general belief that 3bar skills are the most powerful, but there's also efficiency, as in the 1bar that does as much damage as a 2bar and so forth, so should those be mentioned as well, or are we only looking for the best of the best?