Why do some perks still have inconsistent tier progression?

Ouija

For some reason, there are several perks in the game that don't increase consistently when leveling up. Dark Sense and Bitter Murmur both apply for 5 and 7 seconds at tiers I and II, but for some reason jump up to 10 at tier III. Borrowed Time goes from 10 and 12 seconds to 15, and the same goes for Small Game's cooldown, but in reverse. Ace in the Hole's rarity for finding an add-on is 10, 25, and 50 percent. Blood Warden goes from 30 and 40 seconds in its first two tiers to 60 seconds at its third.

This is a detail that's always bothered me. I know it's a relatively minor issue, but is there any reason there shouldn't be a smooth progression between levels?

Potential adjustments:

Dark Sense/Bitter Murmur - 6 seconds base; 6/8/10 seconds after last gen

Borrowed Time - 9/12/15 seconds

Small Game - 15/12/9 seconds

Ace in the Hole - 10/30/50 % chance for Add-on

Blood Warden - 30/45/60 seconds