I don't recall ever claiming that Oliver is a good leader. He's a mediocre (at best) tactician and gloryhound who does more than anyone else we know of in the NCR to ensure the NCR will be defeated. I'm just pointing out his overall strategy that people just assume is bad because it's Oliver or House said so is correct. And I'm still not sure why you think you can just assume Oliver has no plan beyond defending the Dam but the contrary requires evidence.
Let me put it this way.
There is a forest filled with unicorns somewhere on the planet. You may say "prove it," to which I can say "prove there isn't!11!"
This is exactly what YOU are doing. That goes against all logic, because you're requiring me to scour the entire planet and catalog every location on Earth and make SURE there isn't a unicorn forest. And even when I come back, you can just claim "you missed it, check again!11!" On the other hand, to answer the question "prove it," you need only to point at the unicorn forest.
Same philosophy here. I'm asking you to prove Oliver has a backup plan, you're saying "prove he doesn't!11!!" Uhhh, HOW? I've played this game multiple times and I've never seen a single piece of evidence in game that suggests Oliver is a brilliant leader with a plan B and an ability to adapt. I can't SHOW you evidence because the evidence is the non-existence of the evidence YOU should be presenting. Hence, why I sit here and ask YOU to present evidence. YOU have the burden of proof in this, not me. YOU are trying to prove a positive, I am trying to prove a negative.
The person who's trying to prove the existence of something has the burden of proof. You will never hear a murder trial where the accused claims the victim had a pistol and was about to shoot it, the accused is asked to prove the victim had a pistol, the accused responds with "prove he didn't1!!1" and then the entire court says "whelp, he's got us there. Guess he's innocent afterall. Lunch anyone?"
Another thing, this is a piece of literature. Statements made by characters in game are basically intended to be taken as fact UNLESS there's evidence to the contrary. For example, Lanius' bio is a case where there's evidence of the contrary. We don't know his true story because the developers purposefully provided us with info that seems to be self-contradicting, suggesting there's myths about Lanius floating about.
Oliver? There's not a SINGLE opinion suggesting Oliver is awesome and he's got this. There's several suggesting he has no clue what he's doing and there's several opinions and in-game actions that show examples of the Legion having their [censored] together whereas the NCR just sits about with their thumb up their ass and acts surprised when they get beaten. Why would the devs design their work of literature this way unless they were trying to get the message across that Oliver is ineffective and the Legion did their homework? They wouldn't, every in-game opinion voiced by a character has a purpose, and they all seem to point towards the NCR and Oliver being ineffective whereas the Legion is pro at waging war.
And one of the issues the NCR has, suggested by in-game opinions, actions etc. is that Oliver isn't flexible. He's willing to throw away lives while focusing solely on glory, is focused only on showing off his Heavy Troopers and outshining Hanlon, and has presented nothing but a basic defensive positioning at the dam. Countless NPCs (House, Ulysses, Caesar, and possibly Graham and some random NCR vets, unsure of those last two) suggest that there's no way Oliver would ever be able to match such an ingenius tactic as the one presented by Chief Hanlon, and thus the NCR may fall because the wrong guy is in charge this time due to a corrupt government and chain of command. The NCR was literally on full retreat up until Hanlon pulled that idea out of his ass, with only the 1st recon and the NCR Rangers still standing. Had Hanlon not been there, let's face it: NCR would've lost the First battle. At least, that's the implication I draw from it.