Yes I love a good story arc when you have to opposite camps need to work together to defeat an even bigger evil, And you know what? You keep on that Eren stan, cause who knows what might just be in the end . (not a spoiler, just a theory)
That Armin thing bugs me! I was one of those who tought it should've been Erwin saved. I know Armin is one of the 3 main characters, but every action Armin did only showed that if it was Erwin, he would've handled that better! Armin is young unexperienced, emotional, and doesn't have much time to gain all of that. All I hope is that all this L's would build up to his greatest W, otherwise that move was a big mistake on the show's part, but I trust that the show knows what it's doing.
If you're really interested in seeing a live performance, here's a clip, the band is called SiM: youtube.com/watch?v=Z7-XFsAYVt8