Cards aren't categorised into Rare and Common by their Quanta-comsuming effects. Funnily enough, it's by the actual effects of the cards. Miracle is very often a LOT more useful than Fractal. Look how well Light is doing in the War, that is a lot down to Miracle. That's why it's rare, it's very powerful. Not because it consumes all quanta. You're argument has no substance.
Your argument: It's rare because its very powerful.
What is made out of that: Zanz intenionally created an overpowered card and made it rare.
My argument: The only thing that distinguised miracle from the rest of the cards is the fact that it drains all your quanta which is why it is rare. What other reason would there be?
Exactly, Zanz didn't want all the cards to be of equal value and power, so he made some powerful ones, but made them rare. The fact that it drains all :Light Quanta is not what distinguishes it. It's ability does. You would most likely use miracle when you have about 20 health or so, so it heals around 80 when used. Now a card that heals 80 is VERY powerful, so to balance it slightly, Zanz made it drain all Light. However, that is just so it isn't too overpowered. Fractal, on the other hand, is not very powerful. Sure, it's powerful, but not in the same league as miracle. However, if it didn't drain all
, then it would be obscenely overpowered. He added in the same effect of Miracle to balance it. This does not necessarily make it a rare.
Another example is Titan. Now compare it to a Sapphire charger. Most people would use Titan because of it's Momentum, but if Titan is a rare, why not make Charger a rare? There's a magnitude of reasons for this, such as Titan's Hp, it's attack, etc.
What you must understand is that the cards are made rare due to how strong their abilities are. Not because of how they absorb quanta. I can't understand how you don't see that