Viceroys

[-Incorrectish]

Viceroys should have less power than normal feudal dukes. They should give max troops and money regardless of opinion, and should always follow laws regardless ofbeing a dejure vassal. Now you might say this makethe lieges of viceroys to overpowered, and there would be noreason to not use them. You would be 100% right, however this is historical, and a historical way to balance it would be to make a lot more likely to rebel and join factions, which is also historical.

 

[Serenity84]

Viceroys give less troops because they usually have high opinion because of the titles you granted them. Pick some older guy and just repeat. It's sensible balance.

The main issue with viceroys is that they are too happy to revoke things and get into civil wars

 

[SigurdStormhand]

There's an argument for Viceroys having less power over their vassals but not for them always providing max levies and taxes. Holding back troops and taxes was a genuine problem the Emperors had to deal with from reluctant Strategoi.

"Oh, sorry, can't afford that this year" or "Oh, I need to keep all my men inside their fortresses and not send them our over those marauding Muslims.

As to why you have them - it's so you can pick the rulers with the highest martial and stewardship scores to provide the most money and troops in general and also to serve as commanders of your armies. Also so you can pick the ones with the lowest diplomacy and Intrigue so that they have less hope of unseating you.