Basically I’m trying to find an original and interesting story.
For a Night Elf that would become a DH later, is there a compatible point in time where a powerful orc blademaster would be instructed to destroy a village, but due to regret, senseless and honorless murdering would decide to leave the horde, save a child and raise him as his own ?
Besides the moment orcs fight the night elves during WC3 it leaves a too short time window to let the kid grow and join the Illidari.
Was there any other interaction between the two races before ?
The Horde did invade Quel’Thalas during the Second War, so maybe a High Elf could be plausible, though not sure how they’d become a Demon Hunter. They also destroyed much of Lordaeron, including Dalaran, so it’s entirely possible there were High Elves living there as well.
Night Elves were first encountered by Thrall’s Horde (and anyone else from the Eastern Kingdoms) when they sailed to Kalimdor during the Third War, so there’s no real way one would appear any earlier.
If you want to be really clever with it, the Horde DID sail to the Tomb of Sargeras during the Second War; and we now know Nightborne and such still live live there, so you could maybe do something with that.
Can I ask what wrong with the default DH backstory that doesn’t make it “interesting”?
I feel there’s room for personal input, mainly around the the process of becoming a DH. Was loss the drive? Perhaps it was felt a calling? Desperation for revenge?
See how you answer this and focus on adjusting to something you like, as I don’t think orcs have had much beneficial contact with night elves for something like you suggest to happen.
“Honour” and “Duty” are traits not restricted to orcs. These have been demonstrated other races, evident with the existence of the Wardens vigil with night elves.
I think you’re on the right track going with an assassin, but my point was: how is this going to shine through your character now?
My main advice would be to not make the backstory too complicated. It makes it difficult to RP with and doesn’t really add much to the character.
If you’re wanting a night Elf to be raised by a Horde faction, the only plausible one I could really see is Tauren and even that is pushing it a bit. To be honest it’s probably better to just avoid the messy back story. Not all back stories have to be something that has never been done before, a Night Elf just being a night elf and then demon hunter is fine.