Nobody seems to offer any feedback on my suggestions, so I'll just come right out and ask for it. My poorly defined modus operandi at present for retagging is that that tags should be about how to do/play something ("body of knowledge"; and this is also why game tags are good), not simply be about some static/elemental thing. While I'm still trying to turn my thoughts into a truly meta-worthy wall-of-text, I'll try to bait some arguments to see if I'm sane.
Here's a couple recent retags of mine and my rationales:
Added class tags because these questions are about how (class) works. These tags are also specific ("subtags"), because a sniper in TF2 has nothing to do with a sniper from Battlefield.
Didn't add a class tag. While they're about medics/spies, the information is equally valid for all TF2 players, not just a class.
I also hate redundant/overbroad tags:
Removed stealth. Redundant with it being tagged as spy (should be tf2-spy), as it is an absolutely essential mechanic of the overarching tag.
Furthermore, by this logic I abhor most uses of weapons, e.g. here. All soldiers use weapons and in TF2 that's pretty much how classes are defined, so what's the tag really add (when in doubt, throw it out)?