It could be that I just got lucky throught my playthrough, though, to be honest, the thing I relied most on was the basic set of skills the Galak Z comes with. Super boosting with R1 and pushing Square will make you dodge pretty much anything and I found that being aggressive with the mecha to be pretty effective. Basicaly, charge the sword and boost through and enemy, slashing while passing it. You'll be safe on the other side, ready to charge again and get him before he's able to react. It's very good agains the more nimble adversaries that show up later.
Having said that, I may have expressed myself more negatively than I meant to when I spoke about the difficulty. I do admit being a tad disappointed about it being over so quickly, but I guess I only feel that way because I enjoyed my time with it. It just feels good to float and boost around, using the environment to kill the enemies (specially luring them to those spider things that hide on the rocks) and such. I guess I expected more, but it was an enjoyable game.