I always applaud companion content to a beloved story, so I was kind of having high expectations about Halo Legends. Unfortunately, it all felt really cheap and uncoordinated.
You get seven animated stories in two hours, with various animations styles, various directors and so on, made by Japanese animators. With the considerable talent they've got over there and the resources of 343 Studios and Microsoft, this should have been amazing. Instead, the 2d animation felt like some 1980 anime and the last one, a 3D animated segment that looked like made with the Halo engine, was pretty weak.
But the problem was not really the animation, because I don't care about that, it was the stories. There were not bad per se, but they were not even close to special either. Probably the one with the Arbiter was one of the best, but the animation style was weird and took me out of the story - also it needed a lot more context to be understood, even if you know the lore. I liked the sniper mission one the best, but the childish dialogue again ruined it.
Bottom line: some entertainment value, but ultimately cheap looking and boring.