Warriors Combat/Battles.

Power scaling is the death rattle of a series, it should not be advocated for because it then leads to this sort of climb to the top where top tiers are utterly untouchable and it's impossible for anyone to get lucky or win with good preparation if they're of a lower tier.

Also, protagonist plot armor doesn't seem to be a huge issue. Considering Firestar and Hollyleaf both died of their injuries despite winning the battle, Cloudtail got messed up by Darkstripe, Sorreltail presumably was killed by Darkstripe, Brokenstar easily disposed of Ferncloud, Darktail sent the clans packing, Blackstar lost a life, and so on and so forth. The fact that Ivypool defeated a couple of jobbers and Hollyleaf and Firestar had to go beyond their limits in order to defeat their enemies doesn't scream this. I think what you're complaining about is more just the atmosphere of the books rather than the outcome of the battles. I'd also note that Dark Forest training is great and all but the only people who say it's great are cats who have already been in there and would of course hype it up. Every other clan trains every day too, after all, and the Dark Forest only just organized. Dark Forest cats are also as a whole generally a more cowardly, traitorous, and less trustworthy lot, which means team play can be difficult(see them all bolting the moment Brokenstar dies).

Anyway, the gold standard for battles was Scourge and Firestar's duel. It was a good back and forth and very visceral for both. Tigerstar vs Firestar also is pretty good, though it could do with less cutaways to the audience and less of a turn-based feel. Admittedly some of the fights have been disappointing, like Hollyleaf's happening off-screen and Ivypool being a great big ball of disappointing hype, but still, not bad over all. All of Darktail's battles are excellent, for example.