I have this module fully ranked, and it says it tags enemy while looking through a scope.

When I see someone through my scope, it tags them for me (puts a red dot over their head) but they are not tagged for my teammates. It's sort of a useless automatic tagging if it's only for you, and the tag doesn't last as long as a normal tag (where you go into visor mode and tag people).

Is this working as intended?

Visor Enhance (at its core level, and even at the other tiers) never tags anyone. (The 2nd tier protects from flashbangs, 3rd reduces energy of Nanovision according to some other site).

Visor Enhance's only purpose is to make it easier for you to pick out enemies when scoping. The red allows them to pop out against backgrounds that are almost always green, blue, or tan. Plus, it is super useful when they are behind foilage, or even if you spot them and they hide behind a wall, you can see them faintly through the wall! I use it with my sniper class and its great.

Tagging, a different thing entirely, is something you will need to do manually if you want your whole team to benefit. Cause think about it, if visor enhanced automatically tagged people you spotted, if many people used it, you'd likely know where every single person is at any single given time, which isnt any fun and SERIOUSLY would defeat the purpose of cloak mode.

So long story short: Yes, your Visor Enhance is working as intended.