How does the frquency of random encounters work?

[hydralisk2]

Hello, I have been thinking why some encounter events repeat over and over, but some rarely happens.
Especially "Rust Devil" events that are just over used, and make some unique NPC extremely hard to encounter.

Let's say, if I want to adjust some events' frequency. Specifically I have made a pretty challenging "deathclaw buff" mod.
(Better combat style, perks, higher stats and speed, resistant to all explosives, and immune to limb damage.)

I am very satisfied with the test result. Then I changed the priorities of all deathclaw encounter to 100.
However, I barely encounter any deathclaw in game.

Is there some tricks to change the frequency of random encounters easily?

For example, I want to make deathclaws spawn more often from random encounter (especially ambush), not settlement attack though.

 

Thanks!