I agree that Reva could have been better portrayed as a villain (unless she evolves into an anti-hero or something), but Obi Wan is kind of out of shape and he clearly is not the same Jedi we saw in ROTS.
He was barely able to use the Force to save Leia. His connection to the force is weak (it reminds me of Kotor games when you start your hero's journey with Revan / Meetra Surik lol).
Actually, it is safe to say that Reva ironically
saved his life when she stabbed the Inquisitor, cos I don't think Obi Wan would have been able to beat him in his current state.
All that said, I'm very excited to see how he gets stronger for his imminent encounter with Vader, and not just in the supernatural or physical aspects, but also in the emotional ones. He really looked broken when he found out that his apprentice was alive.