Even with clarification like that, we still have some problems:
1) BiS leather gear - some leather items can be BiS for warrior and rogue, or paladin and rogue. What about the situation when "Item A" dropped, its BiS for War fury and combat rogue. Rogue needs it ofc. Should War need or greed on that item?
2) Same goes for some trinkets for me. An cool trinket dropped in icc 25. Its Bis/Pre-Bis for few people. But, its not Bis or pre-bis, but still viable option and upgrade for even more. Should the 2nd group greed on that trinket or need?
3) Classes that can equipes multiple types of set - like paladin, cloth, leather, mail and plate. Lets assume he is healer, he is doing icc. A very good cloth dropped, some cloth classes needed it. Should a paladin (and druid and shaman) need on it, or greed?
I'm for clarification as well, like You. But it would be really hard to clarify these rules, making some serious amount of people mad about its current state, everytime.