Not sure how theres a design flaw. BotD is a resource that you need to manage, just like many other systems in this game. The Dark Arts system is like this as well. Yeah the cooldown is only 5seconds, but if you use it every time off of cooldown then you'll quickly run out of MP, which results in lower damage and locking you out of some abilities.

These new systems encourage you to be strategic in how you consume and renew these resources. THATs where the challenge lies. If you want to completely get rid of these systems then you are just asking for simple/easy mode.