If you're clearing each instance and gaining 224 gear, call the 220 stuff irrelevant like we do. Use a suicide loot list. People get what they want, the mats go to the guild bank, and Ive used ours to make hilts/barrels/relics for toons that dont yet have 220/224 stuff. Eventually it will get to a point where the mats wont matter as much, then i just random that stuff. Honestly I think you're putting too much thought into fair loot distribution.
Obviously what Ive said here applies to guild runs, if you're pugging then just master loot that stuff and everyone gets 1 224 piece each, the losers get the purples mats even distributed between them.