I think the feature is just there for namesake. It won't do anything, even on matchmaking (most ppl use it to report SP tanking builds, like rank 6 epics and legendaries in a 5k SP lobby). Ig it's used as a means of distraction to calm ppl down when they face insanely overpowered mechs and weapons :)

I also had the same doubt, but I assumed the aforementioned guess to be true, and it didn't bother me (though the habit of clicking report after being busted by maxed out killshots never goes away)

Valid concern. If indeed most people are using the Report button against tankers, then reports against actual cheaters (those who use modified game code, etc. to change actual game behaviour) could get lost in the noise.

Its just there for show to make it look like they care about fairness, but it doesn't do anything