User blog comment:XGlass Reflection/Series Discussion~ Favorite Death/@comment-23811814-20140113175552/@comment-179280-20140118225150

I think the issue here is not that they are expendable, but how. In fact, Mike's and Petra's deaths were practically for nothing but to show how merciless and unexpected the SnK world is. Hannes' death was also unnecessary, but since it served as the cathalyst for Eren's Coordinate, it kinda had a point.