Maximum amount of linked keywords for Tier1 content?

I usually just go with one keyword for my Tier1 as an anchor text but I'm wondering if that's just waisted if I could use 3 keywords instead. Would it dilute the effect in Google algorithm between all those keywords or are they equally valuable?

There is no perfect equation or ratio.
If your post has a high density of targeted keyword your tier1 should be most of the time generic.
If it's low/ very low you can be more aggressive with using your keyword in anchor text.

Google either will figure out what your page is all about based on anchor text or keyword density in your post.
As I said, there is no perfect equation or ratio just keep in mind high on-page keyword density and high keyword anchor text = disaster. You need to play with it carefully to figure out what will work for you.