Need is for main spec, greed is for offspec. He was a douchebag and needed it. We dont need a system to police need/greed. People that need everything always gets whats coming to them.
This isn't a hard concept since I don't know why you seem to think it is fine and dandy as is.
WoW instituted a 'cannot roll need on items you can't effectivly use' for a reason, because there ARE people out there (a large number actually) who will roll need even if they have exactly ZERO use for an item, just cause they can.
Light armor should only be available as a Need roll to LIGHT armor wearers.
Same with medium, same with heavy.
Tokens for gear should be only Need for the classes that are listed.
It is simple enough to go "hey STR item, only needable by STR classes" and the like.
All loot still has greed button.
Believing that karma and 'it will come back at them' is fine and dandy, but that doesn't make loot magically appear back to someone who actually could have used it.