I recently started playing Viper, and I have to say, she's very good. Her ability to block pushes and just defend a site is incredible. On attack. I would say that her wall is much better than any omen/brimstone smoke to enter to a site(on split, you can block CT with the poison orb, and ramps and the entire heaven with her wall on A). You can do amazing executes. She's also amazing post plant, and if she has her ult ready, she's almost invincible post plant. The advantage the viper pit gives you is just too good.

Maybe it's just because I'm in a low rank right now. But honestly, she clicked with me instantly, feels so good to use her. If you know lineups, executes and one ways, I think Viper is incredible. She's not the worst agent. That's for sure.