Card Balancing Question

Not sure which flair to use, but discussion seemed to be the best fit for this.

I have been dabbling in concepts for custom characters in hopes that once support is there to make a custom character for StS2 I can have the groundwork to get started on the code and not have to worry about designing cards later.
The question I have is that I was wondering if there is any sort of "Value Point" system in StS or StS2 to determine what is balanced and what is overpowered?

Example: the basic starting cards like strike and defend are 1 cost with 6 attack/block. If you Gave every point of energy an allotment of, let's say, 10 VP then since the cards are basic cards they get a x.75 multiplier to land you at 7.25 VP this would make the base card just under, but the upgrade would be above if each point of damage/block was equal to 1 VP.

This would also mean that keywords have different costs and payouts. Typically positive key words subtract VP and negative KWs would subtract.

I've been trying to find any sort of logic but I keep hitting inconsistencies. So I am not sure there is any sort of system like this used for balance. Or if there is, I am missing a chunk of the equation.