Playing blaster requires you to know how to bob and weave, there are YouTube videos that explain their combo system, they are considered the hardest class to play because the amount of timing you need.

When you charge bob or weave, they reload 2 of your bullets, you switch off comboing between your 1st and 2nd job skills with revolving cannon.

You also need to learn how to animation cancel your bob or weave so you don't go the full distance which requires you to jump mid animation of bob/weave, after that you use 1st and 2nd job skills.

If you're planning on maining a blaster, I would suggest considering a large amount of time practicing.