Hi Naamah! Thank you for pinging me here.
For me personally, I will go back to an anecdote about the first rare spawn I encountered (and still pay homage to @ my transmog) in Vanilla: Nimar in Arathi Highlands.
The drop rate was high for this green compared to rare drop rates now, and I was so stoked upon getting Nimar’s Headdress for my little undead shadow priest. You always got a green item (the ‘rare’ drop) and the loot table for some rares as I recall had very specific items like Nimar with his headdress. The headdress was 80% drop rate if I recall with an eight-hour respawn timer.
I believe that sort of higher drop rate needs to exist to maintain the novelty of a ‘Rare Spawn’ and its subsequent rewards, paired with a longer respawn window so these ‘Rare Spawns’ actually feel rare. Even more of a bonus if not locked in the current FOTM max-level zone. Thank you for hearing me out!