You're missing a very vital piece here, these two pieces actually work quite differently...
Darkvision, out to its range, allows you to see in Dim Light as if it were Bright Light. It also allows you to see in Darkness as if it were Dim Light. If Darkvision actually made Darkness like Dim Light to you, then Darkvision's other feature would let you see in it as if it were bright light. Thus, the ability to see better in Dim Light doesn't help you if you are actually in Darkness...but can see anyway because you have Darkvision.
Darkvision works as follows:
You can see in dim light within 60 (or 120) feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.
The structure of this sentence is fairly important and has been clarified by Jeremy Crawford, the lead designer of 5E.
Q: Darkvision specifies that you see dim as bright in 60', then says you see dark as dim. Is that also 60', or unlimited?
A: All of darkvision's benefits are limited by its radius.
Thus, for further clarity, a creature with Darkvision can see in Dim Light as if it were Full Light within 60'. And can see in Darkness as if it were Dim Light within 60'.
The Eagle Totem feature says...
You gain the eyesight of an eagle. You can see up to 1 mile away with no difficulty, able to discern even fine details as though looking at something no more than 100 feet away from you. Additionally, dim light doesn’t impose disadvantage on your Wisdom (Perception) checks.
Again, looking at the structure of these sentences, this feature does two things.
- Can see fine details of objects up to 1 mile away as if they were only 100' away.
- Dim Light does not impose Disadvantage on Perception Checks.
Thus, someone with both of these features combined can do the following.
- See in Darkness out to 60', taking Disadvantage on Perception checks.
- See in Dim Light to an unlimited range without Disadvantage on Perception checks.
You do not have unlimited range vision in the Dark because Darkvision only works within 60'. You still take Disadvantage on Perception Checks in Darkness because it's Darkness. The fact that you treat it like Dim Light doesn't make it Dim Light. It's still darkness.
Darkvision does not actually turn Darkness into Dim Light. You are still in Darkness, and so the Eagle feature can't see in it.