Normal / normal is too easy, but very hard battle difficulty is extremely annoying due to the unreasonable bonuses the AI gets (your advanced infantry units will get beaten by militia in a melee).

To make it a real challenge, set campaign difficulty on very hard and battle difficulty on hard. If you want to truly enjoy the magnificence and might of this glorious empire I would recommend you to fire up the world domination campaign, which means you have to hold 40 regions by the end of the year 1799. Therefore the short campaign (capturing 11 more regions by the end of the year 1750) is just too petty undertaking for this 'faction'. Restoring the (Holy) Roman Empire seems like one badass goal. Difficulty depends on what goals do you set for your campaign.

Royal coat of arms from left to right: Kingdom of Bohemia, Kingdom of Hungary, Kingdom of CroatiaĪlmost everyone who played a bit with Empire: Total War thinks that Prussia is the hardest faction.