Should voting on a post with many votes dilute voting power the same amount as voting on a post with few votes?

The way I'm understanding things, the current system only favors voting on good posts or comments which have very few votes. This is because you are trying to vote on something good before others do. However, the result is that voting for anything with more than a few votes is not a good use of voting power. Even if I find something extremely insightful or interesting, I don't want to vote on it unless I can get in early (otherwise, I'm wasting the power of my vote). This means that the vast majority of posts won't get any attention. After a post has been discovered, what incentive is there for it to garner any further votes?

Would it not make more sense to dilute voting power slightly less when voting on something with many votes rather than when voting strictly for the purposes of curation? Could there be a second type of vote which brings more attention to a post but doesn't dilute a user's voting power? Just to be clear, I believe my confusion is due to my misunderstanding of the system rather than any flaw it might have. Could someone please explain where the error in my reasoning is?