Astra works great on a team with Viper because they are both smoke/toxin agents. They have the ability to work well off one another. If Viper has used up all of her toxic fuel, Astra can step in to throw up smoke walls. And vice versa, when Astra can no longer pop smoke and Viper has had time to recoup toxins, and she can reactive said wall. It is not advised to only have one smoker agent on a team, so teaming up with another smoker agent is always a wise choice. Sova also works well paired with Viper. When Viper puts up her Toxic Screen, Sova can use his Recon Bolt to dart behind her smoke-screen of a wall and find enemy positions. Having both of these agents on one team makes their abilities used in tandem deadly for any opponent.