If this was an origins story, it would be okay for it to be a little slow or out of place at times. But it's a stand alone (even though at the very end of the final episode they leave us with a tantalising scene of what could be coming) there has been no news of a second season or even a film to complete the massive backbone story arc. Disapointing.
It's alright with some interesting quirks. Though it did seem to be more of a prelude to the main event instead of having the strength to be on it's own.
Watch it in your own time.