iirc the level requirements go along with the treasure maps mentioned.

When I was leveling a warlockteam @ lvl 91, I stumbled upon a hut with a treasure chest inside, tooltip suggested nothing but like "click to open" but there were no level requirement mentioned, so out of the curiousity..

I logged off one lock, made a lvl1 toon, which I then summoned next to the chest. Hovered the chest again, and it had an additional text "requires level 91"
I believe every toon is equal getting any loots from the rares, but the gear usually have the level requirement, so it's useless to loot lvl 92 gear for a lvl 49 toon :>