So what you're saying is, different classes and specs have different mandatory covenants that you should take. I see.I honestly don't know what point you are trying to make here. In a choice between classes you are comparing the various potential classes. In a choice between covenants, you are comparing the various covenants. The covenant choice being a level down doesn't change the mechanics of the choice. In one you have a power-flavor/aesthetics-story-gameplay choice that makes you better or worse than people who choose another choice. The the other you have a power-flavor/aesthetics-story-gameplay choice that makes you better or worse than people who choose another choice.
That the second choice is within a class, if anything, makes the comparative impact of it less. Because someone playing current fire mage and picking a "bad" covenant is still probably going to perform better or in line than someone picking WW and picking a "good" covenant. An absolute minimum fire mage parse still lands in the average range for WW.
Now you are just undermining your own argument by pointing out that the relative power of the class based ability isn't even defining, because there are secondary factors like general covenant ability and soulbind options. Yes, that is part of the point. There are many factors to the choice, that is what makes it interesting. What resto druid is going to give a shit about a 60s CD blink with a cast time when they can take a literal beacon of light talent? Kyrian priests get a 50% movement speed baked into their kyrian active. A 90s CD 30% sprint might be very attractive to low movement classes, but it's significantly less attractive to people who already have a lot of mobility.