Definitely pairs for Babel.. Single is just too ridiculous, and it seems like Axis Mundi was still "broken" as well. It took two days of trying it, but I finally managed to beat it! The challenge was well worth it though in my opinion.. and like you said.. It's all do-able. When you reach the end of Axis Mundi and are about to climb up to the finish, it's an awesome feeling!
Till The End