After patch 1.8 and 3 expansions and with 1.9 around the corner promising to bring even more rebel fun because it seems pretty much no one will be able to escape a civil war per game... anyway I digress my point is that after all of this I still see the UI lying to me on a regular basis regarding the amount of diplomatic power needed for a given peace deal. Is it too much to ask that this trivial issue be fixed once and for all before you guys can focus on what is really important like bringing even more rebels into the game?

Thank you.
here are my observations based on my WC run:
conquest CB (yours) - anything you do on a province you have claim on is 0 dip (whether you're taking for yourself or gifting it to vassal), other province is base 50
conquest CB (vassal) - all provinces base 50
reconquest CB (vassal) - anything you do on a province which is the vassal's core you declared for is 0 dip, other province is base 50
imperial ban - all core return + conquest of imperial provinces is 0 dip
imperialism CB - every province is free in main peace
separate peace is always 50 per province (have not tested in case of deus vult)
Hopefully they will fix it (fingers crossed).

Previously there was no LA requirements and now it seems that above 10% average LA (very easy unless you are huge at game start or do nothing) and low legitimacy (random and rather common) you're in trouble. I hope I am wrong.
I'm not a fan of making things even more dependent on the rather un-transparent RNG-heir mechanic which given the common occurrence of heir deaths is near-impossible to control - regencies are already punishing enough.