I mean, no noted conflicts vs no conflicts are different things. The Night Elves and Tauren had issues with each other, as per the Scepter of the Shifting Sands. And while CDEV did say that Maiev was exaggerating about exterminating races, they did say they had gone on campaigns of Total War, and the Satyr were just one example.
In addition, the War of the Satyr would have been doubly draining, not just killing Night Elves, but then turning them into Satyr. Triple dipped, if you count the plague of Worgen that resulted from the Pack Form. You also, as you said, have the War of the Shifting Sands, which was also a continent spanning war.
Then you had the 3rd war itself, where the Burning Legion marched through Ashenvale.
While it’s a myth that all the men in Night Elf society were druids and were all asleep, even with a male population to reproduce with, they’d been in 3 potential apocalypse level wars that we know of.
It’s not really that surprising there aren’t that many when you remember every one of the major conflicts we DO know about was the type of “If they lose, the world ends, so they can’t lose”
Like, it’s no a stretch to say those wars were on a similar level of some of the expansions, and some of those wiped out an entire generation of Orcs.
EDIT: I will say, I think it’s exceedingly messed up that Blizzard acknowledges Night Elves are ready and willing to participate in Total War, but then never show them doing it against the Horde in Ashenvale and beyond. It would have really made the whole Night Elf/Orc conflict feel a bit more grounded when the end result of picking a fight with Night Elves is they do a little bit of war criming.