It's easy to steamroll with any nation once you get momentum. I was complaining about things that seem really disproportionate (i.e peasant rebals spawning in numbers at my force limit and what the hell, it's peasants, not ninjabikers from Mars), things that seem really disproportinate (I think coalitions are a fine mechanics, but not when they send armies of hundreds of thousands against forty thousand etc) and things that blindsides you and reams it far up once you're on your knees (i.e enemies allying great powers during ongoing war and calls them into the war). The majority of people responding in this thread have loudly offered their disagreement; some have offered advice; a select few have even sympathized with parts of my complaints.
I enjoy fighting wars on epic scales where the rewards are exceeded only by the risks. If I am preemptively attacked by Austria and Venice, I want to be able to gain -something- from that war without facing retribution from half a dozen other nations. I do not enjoy watching my armies crumble at the hands of rebels, because rebels are an artificial hurdle to overcome, an obstacle without substance, a drain on manpower and gold instead of a real entity with an agenda of its own. I do not enjoy random events destroying my only ally against France, nor do I enjoy watching my army shattered and wiped against an opponent that has less moral and troops than me.
People assume I complain because the game is not as easy as it used to be, when I in fact am complaining because I tried a whole bunch of starts that just spiralled out of control in ways that I never experienced in previous patches. Want to make this game harder? Try things where player choices are more important than RNG. What if diplomatic actions didn't show numbers, but instead scaled from 'No' -> 'Unlikely' -> 'Possibly' -> 'Likely' -> 'Yes'. What if diplomats had stats just like rulers and generals, and could offer promises of gold, manpower, or claims in return for royal marriages, alliances, or peacing out earlier from wars? What if battles were simulated without being open to expoits, baiting, and general gaminess of the players? Make armies work like explorers/conquistadors, sending them on missions to conquer areas, to reinforce nearby troops, to retreat, or to attack enemies. What if armies were built with a specific composition of troops in a region and arrived as a single unit of 'small', 'medium', 'large', or 'massive', each with its own benefits in terms of speed, attrition, etcetera. Talk about grand strategy of gaming, instead of grand gaming of strategy.
Just finished a ten year long coalition war that included France, Spain, Austria, Venice, Genoa, Hungary, a handful of minors, etcetera. Why? I took two provinces from Portugal and vassalized what was left of Aragon. It was a brazen move, certainly, but it just doesn't seem historical or balanced gameplay-wise to unite half of Europe against a single nation for any reason. I don't know. I'm going to let the issue drop for now and just go back to my corner.