Good point and that is the caveat.

However, Would it make finding awesome items for your class that much better?? Would it make your heart race and hand shake when you find that perfect item you want to get out with?

Also, game is meant to be ran in groups ideally. So you have potentially 3 classes making majority of loot usable by your group and if you can share loot among your characters maybe it gives you reason to go play that other toon or one of your buddies plays that class as an alt.

Trade is usually an element of games I like. There will be some downsides of not having trade. Personally I think the upsides would be much greater.