You misunderstood my notes. Under A vs. B I didn't compare two things that could be done in the same moment of the game but two different situations that lead to the same conclusion under your system. For example making 1 Wd on a model doesn't worth a 7+ card in your system whether it is from 10 to 9 or 1 to 0.
However "real life" is usually much more complicated. In my book the later case would even justify burning a 13 if that model is a serious threat with its upcoming activation(s). And there are many-many more subfactors (strategic goals, placement, activation order, needed cards for spells/triggers to go off (X+ numbered and/or with a certain suit) etc.) that you should take into account when you need to decide to use or not to use certain cards from your hand.
So all in all I just have a feeling that this base system needs so much in game tweaking that it is probably a waste of brain cells to bother with it. Or to put it in other words: I think your good results are more about your game knowledge, tactical skills, intuition and stuff than this calculation method.
Please don't take this as a malicious critisicm or something. I just wanted to share my thoughts with you.