From a singular player's perspective, this lowers raid loot by a bit (assuming not all raids are filled with 12 players)....from a guild or group-oriented perspective, this hurts teamwork. No longer are you part of a team deciding in democracy who would best benefit from loot....each person is their own agent now, giving 'possession is 9/10ths of the law' rights to loot before it can be decided upon.
I don't like the new system in 2 ways, listed above. I do like it from the perspective of a solo player, but raids aren't about solo players...they are about groups that work together. I would like to see them lower the rate of this system and add it on top of the current system. Each player gets a 1/12 chance of having raid loot under their name on top of 2 items tied to the 2 runes of the current system. You can also add in like 3 chances for random but good loot to even things out (from dropping too much raid loot).
Either way, I think the system should allow for group-oriented decisions that don't put individual players in a bad position (making them keep or donate an item already assigned to them), and doesn't kill any insentive to try a raid with a smaller group. Enough of the 6 man raid vs 12 man raid...a 10 man raid should not be penalized because they are 2 men short. The extra challenge should be enough. Greater risk, greater (or at least equal!) reward.