The independence faction is totally nuts, especially with regards to the Holy Roman Empire.
In vanilla CK2, the HRE will usually have to contend with an independence faction composed of multiple Italian lords and a certain Italian lady, plus some random counts in Burgundy and sometimes the dukes of Holland and Bohemia. That makes sense, I guess. However, since the faction leader is usually the Lord Mayor of Bologna or some such, the Kaiser can simply have 6000 troops march into that very inviting city and gain disproportional warscore for that "accomplishment". The real silliness, however, begins when such merry folks as the Duke of Bavaria or the Duke of Meißen join the independence faction. What gives? Why wouldn't they rather support a claimant to the throne, since every elector within the HRE is eligible as long as the succession laws aren't changed? Why would they claim independence only to be totally cheesed when the Emperor inevitably presses his strong claim and slaps their sorry sitzfleisch? Why wouldn't they try to set themselves up as the Kaiser while the current one is busy with the likes of Lombardy and Dauphiné? Instead, I see stuff like independent Saxony for about ten years before it gets re-absorbed into the blob, while the Salian dynasty switches to Agnatic Primogeniture and rules over the HRE forever. Historically, the Saxons of the 11th century rather sought to replace the Salians on the Imperial throne with one of their preferred candidates (Rudolf von Rheinfelden, most prominently), not secede from the unruly Union and get stomped on by Denmark, losing Hamburg in the process for a net gain of nada.
Let me repeat that: No one in the HRE ever tries to install some claimant or the other. That's because everyone rather joins the constantly-growing independence faction, whose leader declares war at random when the Kaiser isn't otherwise occupied, then either gets crushed or wins by virtue of kinda-cheesy "reinforcements" of similar numbers to the Golden Horde, and then gets crushed ten years later. Even worse off is Byzantium, where every single douxbag always tries to lower Crown Authority while an unbroken line of Doukas emperors reigns supreme for 200 years, since no-one can even usurp the damn throne without a claim. France and England are usually far more interesting in vanilla, since there are multiple but not too many dynasties with claims to the throne, which leads to a pretty turbulent as well as ~*plausible*~ game.
