Charge strat seems to be working correctly, some tests:
100k knights v 100k knights
no strat v no strat = WIN
We managed to kill : 83993 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
But we lost : 77814 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
no strat v charge strat = WIN
We managed to kill : 100000 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
But we lost : 81840 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
charge strat v charge strat = LOSE
We managed to kill : 94450 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
But we lost : 95065 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
charge strat v no strat = LOSE
We managed to kill : 64930 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
But we lost : 100000 Knight 0 Infantry 0 Pikeman 0 Heavy Infantry 0 Archer 0 Mounted Archers
In this scenario it appears the Charge strat's boost to offense isn't enough to overcome the detriment of their -25% defense, so the strat actually works against them badly. A 100% equal force will get zeroed out if using the strat on just one side - with the side using it getting the L, when compared against no strat.
The scenario where charge would be useful is against melee-heavy armies, or when you know you have an overwhelming force.