Just to offer an opinion,
I agree with a small amount of what you say Bacon; A faction's life should depend on whether it is destroyed during RP and not because of Staff verdict. However, raiding is a key part of most factions, whereas it doesn't make any sense for others to do so. Example:
BoS: The West Coast BoS is quite secretive, they tend to stick to their base and perform recon using their knights etc. They would need a VERY good reason to raid somewhere, as they would face harsh repercussions.
NCR: NCR wants to be seen as the peace-keepers and general good guys. They possess a lot of strategic knowledge and want to gain the support of the people. Raiding (ideally) should be reserved for rescuing VIPs or POWs and for pushing into a new area (Hence the Outposts idea I've been seeing).
Legion: Legion are obviously well-known for raiding and enslaving people, but they aren't complete brutes who don't understand the need for it. They raid when they see a tactical advantage (forcing one of the other factions to react, taking over a place of interest etc). In reality the Legion are one of the most disciplined factions, and they raid for similar reasons to the NCR, albeit it isn't POWs, it's slaves.
Enclave: Enclave are a more aggressive version of BoS. However, they are still very much weak and vulnerable, and therefore need to keep themselves from the main attention of the war. Most of the factions want the Enclave dead, so they should only really raid if they want test subjects, or they are taking advantage of another raid (Legion raiding NCR and the Enclave come in to clear up both of them in the confusion etc.).
As always, this is just my opinion. But I atleast hope that you guys can see the reasoning behind most of my decisions for them, since in my opinion, it fits the lore appropriately.
- Kidd.