I think it is clear we have captured fiefs several ways.
We have taken things in huge brass ball moves (see reyvadin, curaw, and recently tulbuk comes to mind, we have also tried it and failed the first run at ichamur, Huge reward... but huge risk as well)
We have used the whittle technique without raids (see Ahmerrad and several others I can not remember off the top of my head)
Now we have started to incorporate some raiding in to mix things up.
All of them have uses. We have war on three fronts at the moment and preserving troops is the name of the game at the moment.