I say Tenshi-centric because the episode only really served two purposes as I saw it. First, where it spent most of its time, it confirmed her human side in showing a range of emotions (concern, remorse, interest, happiness, surprise, and sadness) which also grounded the idea that we should feel sorry for her. Second, it introduced the "second act" of the show in putting the characters it the worst position possible.
And I can see why Otonashi isn't by her side already. He doesn't know anything about this world, and if Yuri is not looking out for his best interests she has established an almost perfect trap. He's been told by her not to get close to Tenshi because he'll be erased, but he's not 100% sure he can trust Yuri. I'd hedge my bets too and play along until I have evidence either way. He hasn't seen the SSS really hurt anyone up until this point so he was safe, not doing real damage, and still able to gather intel about the situation.
And I agree with you, I think Otonashi and Tenshi will have more dealings. I'm actually expecting her to help them out of detention.