Yes, your analysis is spot on – the benefit is not clear enough because the phrase “How to find your business’ online voice” is too complicated (just like one of the bad examples in the video0.
And you’re right about the power words. They need to be concrete to attract attention. Implied power doesn’t work.
Try looking for headlines grab your attention and analyze those first. It will then help you re-phrase your own headline.
Enchant readers. Woo customers. Win business.