Counting damage, mana, creatures, actions, spellpoints... i think that law, order and math are not proper tools to decide, which mage/player is a winner of actual game.
I was thinking about referee as a judge in this kinds of situation. He will listen to both players, their plan for next three rounds, check their spellbooks and then decide a probable winner.
If i will play attrition priestess, keeping my two knights alive, neutralizing all threats and step by step building a point (hold, step, situation) in which i will start defeating my oponent. That moment (point) is not always visible or easily reachable. I fully understand reasons why cannot there be a 2 hours for one match.
Referee decisions like in boxing would be an elegant solution from my point of view. But that will also depends on quality and experience of those "judges".
Statistics or math could be applied if you take all creatures, unplayed attack cards, their mana cost and level and do some cool formula, then roll specific ammount of dice simulating next 5 rounds minus healing effects and armor and apply this on actual live value of mage...