There’s another major factor not mentioned in this article: Conflict cards, which are the action, attachment, and even some special character cards that are played form your hand. Many Conflict cards have a Fate cost.
If you spend all of your Fate on characters, you will have none to pay for Conflict cards, and that could potentially lead to losing conflicts (battles) against an opponent who has fewer / less hardy characters but the ability to play some powerful effects from their hand.
Also, while blitz may not be anywhere near as brutally efficient as it sometimes was in classic L5R (thank goodness), ‘swarm’ is more or less officially stated to be a main Lion strategy. They definitely have cards to make swarm effective, at least potentially: Their stronghold’s blanket military skill focus, their Holding, etc.