After Saurfang killed both rogues in cinematic there is HUGE focus on rogue's eye where is V under it.
Many people wanted to know. It's just random scar or it's symbol? If it is symbol. Who is V?
If you see cinematic. There is no reason why Saurfang do not warned Thrall before they attacked him even he knew about them.
He is only person i remember with name starting on V. Maybe he is more than rebel fighting for honor. Think about it.
Edit: I mean this scar. https://imgur.com/KYWPJyN