Sirius the Jaeger in my opinion had good animation that was soothing to my eye, which is something I value a lot. If the animation was of lower quality then I would most probably not watch it. I didn't think too much of the sound, so I would say it wasn't horrible. It wasn't magic either since I didn't really pick up any traits that were superb.
Now, the story and characters. The story had me intruiged, but due to the character development in most of them made the anime overall less interesting. The characters I became more attached to was the main character, Yuliy and his brother, Mikhail. I wish, however, that they would put more story on the side characters of the Jaeger crew. They had many opportunities to put more traits and story behind them.
I am fairly sure that I would have loved Fallon and Philip as characters. And Dorothea for that matter. They all had such potential. Instead they put in a love interest which was not necessary at all. Naoe. I would rather have removed her and used more of the time they saved and put it into backgrounds to the other characters.
It would be nice to see more background to the Vampires as well. Especially the Elite Vampires and their rulers that we only see once. They could have explained what this virus was as well that were killing off the Vampires. If they did explain it, then it wasn't really hit that much on. Not enough for me to notice at least, and remember.
Overall, I did enjoy watching it. The ending was a nice one in my opinion. I just wish there was more leading up to that point. More backgrounds. In cases like this is when I actually would want some fillers, just to get to know the side characters a bit more.