Yeah, I think Caesar's Legion would be utterly pasted if not for the ridiculous series of bad luck rolls under Kimball.
* The Divide being destroyed
* Oliver's incompetence
* The Brotherhood of Steel battle at the solar energy farm
* The Great Khans fucking up things after Bitter Springs
* The Powder Gangers
* Two of House's gangs planning on betraying him, giving them a chance to royally screw NCR.
IDK about calling these "Bad Luck Rolls" - Most of these are either the Chickens coming home to roost for the NCR, or the result of active planning from the Legion
-The NCR's leadership being filled with psychotic glory hounds is portrayed as a structural issue, not an accidental one - Kimball himself is heavily implied to have his entire career based on expanding into this new province that clearly doesn't want the NCR there - Moreover Boone states that General Oliver himself got his position by being friends with the President, and that he suspects that if Kimball wasn't president, Hsu would be leading the NCR forces - Hell, half of the later NCR quests are done for Colonel Moore who straight up tells you to resolve everything in the most violent way possible - Actually making peace with former enemies - the one thing that would actually stop the NCR's overextension - Is something you have to actively work
against Moore to achieve - Kinda the entire point of the NCR is that the entire upper leadership of the NCR are the worst possible people to handle the job.
-The NCR-Brotherhood war predates their occupation of the Mojave - And massively destabilised the NCR domestically, being partially the reason they're in the state they are now - Having run ins with old enemies isn't exactly a "Bad Luck roll"
-The Great Khans wanting revenge on the NCR for Bitter Springs is 100% the NCR's own fault for massacring pregnant women and children - And it's unlikely they'd be as suicidally attached to Legion had this not happened
-The Powder Gangers are again, 100% the NCR's fault: If you build a penal colony in a land you're trying to conquer, that penal colony rebels, and now causes issues for you - That's your own fault
-The Omertas blowing up the Monorail is mostly due to Legion infiltration, and making an alliance with them. The Frumentari doing covert actions to align themselves with enemies of the NCR, and carry out acts of terror is a large part of why the Legion is so successful. This isn't so much a Bad Luck Roll as the Legion being clever - The Chairmen are kinda irrelevant, since Benny hasn't messed with the NCR yet - And the White Gloves betrayal is again, because Caesar made active efforts to ally themselves with them.
The only one of these that's really a "Bad luck roll" is The Divide. The rest are mostly either the NCR's own actions or past coming back to haunt them - Or Legion being quite clever in their plans to take over the Mojave.
Wouldn't all of those positions require them to be of a mindset different than child soldiers raised to believe Caesar is a god? A lot of cults suffer from losses when they have their people outside of the cult's direct media feed and bubble. The Frumentari in the Great Khans, for example, ends up exposing himself relatively easily.
Isn't Karl openly acting as a Frumentari? Like he will straight up say that Caesar sent him - I don't think he's meant to be undercover.
Everything we see about the Frumentarii in game implies that when they are actually engaging in Espionage, they are extremely effective.
I'm sure there's some ideological yapping about the destruction of the NCR in his dialogue, but honestly I kind of doubt even Caesar would do it.
Caesar believes he's a world historic figure and the fall of the NCR is inevitable. I think he 100% is stupid enough to try.