I suspect the smaller number of provinces and ease of making money has something to do with how easy ETW feels even on VH.

When the Dutch declared war on me as Prussia I was hoping for a few epic battles given they're a major faction but it ended up them being destroyed as a faction in a siege of Amsterdam.
Five turns from being a world power to being a disorder stat in my province details.

My Maratha campaign I purposely stopped myself from attacking the Mughals for years to try and build up a challenge but I'm rolling in so much money I could annihilate them at any point.

A larger number of provinces might give the AI more strategic depth and prevent the easy blitzes by making you have to deal with conquered territories.

Having the army stacks of defeated factions remain as rebels would also be good. Atm you can decapitate a large military force by taking out the faction capital and they disappear.