Terminals are a great way to convey lore and plot that runs tertiary to the main events of the game.

They should NEVER be used to deliver vital information like the identity of Blue Team, or the motivations of the Didact, or the only in-game backstory for the ancient humans. (Which was another HUGE Halo 4 revelation that went relatively unexplained.)

Kal's OP is dead-on. Telling a narrative is just as important as building it.