glassa lot of casters in the tf2 community do a word-heavy radio-style broadcast, but tf2 is the equivalent of tv -- viewers can see what's happening. so casters shouldn't list every single thing they see. during chaotic fights no one can speak that fast anyway.
try to complement what the viewer is seeing on-screen, instead of obscuring it. sideshow was the best at this.
There's a big challenge in making this happen in practice, mostly because the producer has to evaluate what is currently on their screen, what the caster is speaking about, and what is actually happening in the match, to capture what the viewers see.
Additionally, several casters, myself included, do third person view whenever casting, so it becomes commonplace to narrate what we see via bird's-eye, rather than from the first person perspective (for example) of the scout/soldier about to get ubered through a choke. I sometimes try to make the perspective shift so that casting becomes more in tune with the push and (hopefully) the camera, but overall it's challenging to coordinate caster + camera during the cast, concurrently.