My guild does it this way:

Each class votes on a class rep. That rep, in consultation with the other members of his class,
determines the loot order for no-drop class-specific equipment. Whether this is at the individual item
level (e.g., a list for Imbrued BPs is separate from that for Imbrued Greaves), or just a rank order
(player1, player2, player3 - when player1 loots something he drops to the end) is up to the class.

Droppable class-specific stuff is awarded by the officers, usually following the directions of the class
rep.

All multi-class stuff is called by the officers.

If you get an item upgrade, and your old item is droppable, you surrender the old item to the guild to be
distributed to another primary unless all primaries have something equivalent or better.

You have to be actively on a raid to loot an item unless nobody else can (or wants to), in which case we
can start logging on alts and absent primaries.

It sounds kind of free-form and complicated, but it has worked pretty well. Some players have argued that
the officers reward themselves more than is "fair", but I never felt that way.