Are you serious?
A bug and a exploit are two very different things. A bug is something the devs introduce.
An exploit is players taking advantage of a bug or finding ways around in-game rules.
Looting helltide chests for a slot you want/need is not an “exploit”. That is straight up the point. If it wasn’t, they would all be “mystery” boxes. It literally says what you are rolling for on the box.
Blizzard screwing up drop rates is entirely on them. You can’t now magically turn around and blame players for looting boxes which is again part of the gameplay loop of helltides.