From what I understand, in this patch the numbers in the Fixed Strength are basically exactly what they are in the Historical Battle. If you play the Historical Battle of Gaines' Mill, you will see similar numbers.
A basic issue is that this sort of ignores the player's progression or "ramping up" over the course of the campaign. This makes the beginning part hard and the ending part far easier than the regular campaign.
Fixed Strength is very far from being a Very Easy mode. In many ways it is harder since rewards are 25% less, you can get creamed quite easily by overwhelming numbers, and if you start to lose battles you can fall behind macro-wise.