I agree with you about rebels. Reduce them editing rebel spawn to 100 and you'll have a very nice campaign.
It's not fun chasing rebels around your big territories with 4\5 kazaki.
I disagree about difficult of Novgorod as VH. Novgorod is easy to play cause it is really strategically positioned. You can fight Poland\kiev and then face the others. Take kiev fast and you'll have some cash.
Try Hungary, Poland, Byzantium in VH campaing and let me know about it.
However every faction is easy if you don't use some house rules.
Like no save\reload, no pause during battles etc.
And i think that VH is VH ... it is not for everybody. You need to play a little at lower level to get experienced enough to face VH level.
I said that VH is unfair before learning some mechanics of the game and understanding how to win in VH difficulty.
There are factions that are far more worst than Novgorod in VH.
Finally CAI is something that really affect game difficulty cause some CAI will challenge you more than others.