Guild Wars 2

Yesterday my Magic Find was showing as 71%, I’ve just completed an invasion and salvaged lots of items and used the numerous Essences of Luck, yet my MF now shows as 64%.
I regularly play with the same people and they are still on around 70%+

Your magic find stats arent connected to to the people you play with but the amount of essences of luck you consumed.

Your Magic Find stat in the Hero panel shows your actual stat after boni were applied.
To see what permanent Magic find your account has from achievement chests and luck bars filled, check your achievement tab.