With the new patch and the addition of RoE:
100,000 federals in all out attack versus 51,000 rebels in all out defense at level 6 entrenchment yielded a battle result of 72,000 federal casualties. No, that's not a typo.
Be careful with your stances. Thankfully I was playing the rebels in this situation. Unfortunately I don't have a screenshot, but it should be mentioned that this happened at Fredericksburg over a period of several days.
PS: I should also mention that this battle was conducted by randomized generals, and the confederate commander had a defensive value of 10.