I do think there may be some griefing with it however using rift as an example you would need different gear for your different builds my cleric for example needed tank gear and healing gear however i never ran into a situation where people would need on something for an offspec it was generally accepted that you could only roll need for your current spec....i think that most people would either roll greed or if no one had a need for the item they would ask if its ok to roll need for an alt, but yes there are always those few idiots out there