I think if the non-Assassination plots triggered and then you got a series of events over the next few days/weeks/months (depending on the severity of the plot) it could be more interesting.
So you're trying to revoke a Count's title on a county, you get options to try and fabricate your own claims (say, of a long-lost, probably fake but interesting dead relative - i.e. "Well I'm descended from Grandpa So-and-so the Awesomely Powerful, so the land is actually mine!") or you try and prove their claim to the lands as false, or maybe just bureaucratic wrangling (well, actually Count XYZ, you forgot to get your paperwork notarized by the proper officials).
Have a pool of possible events, or possible options to choose that are random so you can't just "always choose the top option" and succeed.
Factoring in the other members of the plot would be nice too. Maybe the other dukes you invited all confront the king at a feast together, and "suggest" he abdicate. Perhaps the high intrigue plot-invite fakes an assassination attempt on YOU, and leaves obvious evidence it was from Count ABC, framing them and allowing you to imprison & revoke on them.
Otherwise, yes, plots just seem overpowered at times, or completely impossible if your dynasty head isn't well liked.