Correctly on First Blade counts but it really turns it from a multi-primary to a single-primarily. can be used for both in both situations, but it's the degree.
DB competes with Prepared now... which doesn't require you to be in-range or not target switching. Any switching hurts demon blades unless you're very careful with your swing timers AND they're always in range, where prepared has no such requirement. Was a much bigger deal when it was competing with Demonic in the prior build, but prepared will still win over demon blades on a movement / aoe fight.