Which bugs are actually preventing you from playing the game ? So what is the gamebreaker for you ?
What breaks it for me:
1. Assassinations. My multiplayer experience was ruined when a King of England (player) assassinated two Kings of France(AI) to stop french-english claim war (France attacked England). I played as a duke of Aquitaine and was really looking forward to have some nice tactical gameplay helping ,my AI liege and avoiding superior english mercenaries.
Also claimants assassinations also makes multiplayer a kind of unenjoyable.
2. Antipopes and prince-archbishops. Currently you can build a great empire by giving duchies to bishops and creating of antipope. even if prince-archbishops do not like you - they will still pay you all the tax. It is an absurd ammount of money. and also you can assign their successors and they tend to be content/humble which gives a nice relationship modifier.
3. Bugs. a good example of such would be - give a county to a bishop located in other county. He will not give it away and will hold one castle and one bishopric. That would be fine, but he suddenly starts to like me less (-30) for holding wrong holdings. That I cannot comprehend. If you do not want to be a count - give it away to someone you see fit, but why hating a liege for entrusting you this choice?
It is minor, but frustrating.
4. lack of plots/ambitions for monarchs. in single player I usually ran out of plots/ambitions at age of 30-40 years. Where are the plots to kill an ambitious vassal? to kill a pretender? to usurp title? to abduct an enemy monarch?
All those were quite historical options, but unfortunately not present in-game for monarchs (some are present for dukes).
5. lack of diplomatic options. I cannot ask a thirdparty not to participate in my wars, I cannot ask elector to back my candidate, I cannot ask a pope to announce a crusade or participate in target selection, if I know about a plot - I cannot notify a target about the danger.