Sigh... sorry, but you're wrong. What you're saying is that games should abandon balance for the sake of being insanely powerful, and that simply doesn't work. An unbalanced game where you tear through your foes effortlessly is simply not fun. Perhaps there are better ways to do this than the mana bar, and there are other ways games have done it, but what you're talking about, unlimited power, simply wouldn't work. Balance is far more important than arbitrarily feeling like a badass: if you want that, go set your favorite game on easy.