Korra did turn to Raava for guidance on one occasion
During Episode 10 "Beyond the Wilds" of the final season of The Legend Of Korra (Book 4: Balance), Korra enters the spirit world to free Jinora and a handful of others from the spirit vines, which had imprisoned their spirits within plant-like bubble pods in the spirit world.
Just after confronting chained-up Zaheer, and after she agrees to let him help her enter the spirit world and essentially work through her trauma, she ends up in the spirit world and you can see the pattern of Raava glow on Korra's body:
Raava lights up inside Korra, surprising her; telling Raava she missed her, Korra asks where she was, and Raava replies that she was always within her. Korra asks Raava if she can help her find Jinora, and Raava transports her across the Spirit World to the missing tourists; their spirits are held captive within a large, green bubble. With Raava's help, Korra frees them; as she does, their bodies are released from their cocoons in the physical world.
-- Summary of the scene I'm describing taken from the Beyond The Wilds page of Avatar wiki
Here is the conversation between Korra and Raava (from the episode transcript):
... Raava lights up inside of Korra.
Korra: Raava, I missed you. Where have you been?
Raava: I have always been inside of you.
Korra: Can you help me find Jinora? [The wind blows Korra to the location of Jinora and Ryu's tour group. They are all trapped inside of a green, spherical force field.] How do I release their spirits?
Raava: You must bend the energy within.
Korra: But I'm powerless in the Spirit World.
Raava: No. You're most powerful here. In the Spirit World, you're connected to all the spiritual energy.
Korra walks over to the force field and puts her hand on it. Her eyes glow and the force field becomes a golden yellow, signifying the release of the spirits.
Cut to Jinora and the tour group being released from their vines.
This, as far as I'm aware, is the only time an Avatar (besides Wan) has directly sought guidance from Raava (and even then, it was more like Raava offered guidance, since Korra only thought to talk to Raava because Raava made her presence known to Korra).