We haven't yet incorporated a lot of our teamwork/communication features into the tutorial, so I'll provide a quick overview of how the "threat indicators" work.
How do they work?
When a teammate dies, a snapshot is taken of the enemy locations visible to that recently deceased player. All remaining living allies get "threat indicators" that point to those last known enemy locations - the closer the location to the viewer, the bigger the indicator. The positions being indicated are not updated as the enemy moves, so it's only reliable information for a few moments, and it's not very precise.
Why are they in the game?
In a perfect world, when an ally dies they promptly share a specific enemy location via voice chat. The rest of your team, simply by listening, can absorb this new info and adjust their tactics to react to the changing game state. These sorts of callouts are critical to making decisions about what to do next.
We've all had the experience where a teammate dies, you say "Where was that?" - and they say nothing. It directly hinders your ability to play, which is frustrating because that information should be available to you. It was fairly earned, but not shared, and now you are at an unnecessary disadvantage just because someone on your team isn't talking.
And there are many good reasons why teammates don't make callouts: language barriers, no mic, discomfort using voice chat online, too tilted to talk, don't know callout names, noisy gaming spaces, or just want to play without having to talk. As some others have mentioned, there are also issues hearing teammate callouts including varying hearing capabilities, voice chat settings, and familiarity with maps.
We made the threat indicators as an imperfect, but reliable, replacement for teammates calling enemy positions when they die. They will never be as good as a well-executed voice callout, but it's better than no information at all in a game where that information should be yours to use, and it can make the difference between a clutch and getting shot in the back.
Please keep playing with it and let us know how it settles as time goes on.