Realm actions are much much different than regular BR.
Whereas in a regular setting Diemed could bring down Medoere in 2 turns by
1. create law, 2. create law, 3. create law, 1 realm contest, 2 realm contest.... BOOM
such a thing isn't possible in RoE. First of all, you don't get a +1/1RP ratio, which creates balance between an AN, major 50 and an An, minor 20, and secondly, for realm actions the basic difficulty increases by +1 for each other holding affected (in addition to having to spend a court action for each additional holding).
Thus, said Diem, having 3 law(0) against Medoere's Law (1)/(2)/3), would have a starting difficulty of 14/15/16 and he'd have to spend GB/RP for each one separately which would be very expensive
Therefore: take it slow and plan for your moves. If you can get other regents in the province (temples, guilds...) to support you you'll have a better chance of success than expecting to overwhelm your opponent with huge amounts of GB/RP
Oh, and I forgot... Contesting a holding doesn't neutralize it like in vanilla, it reduces it by one level only!