I disagree with your assessment of other MMOs. Every MMO's loot system has a flaw. Not going to go into details here. Suffice it to say, that some are too restrictive and some are not restrictive enough.
The solution is actually VERY simple...
If you are in a group, in a particular FP looking for a specific piece of gear, then TELL THE REST OF THE GROUP!!!!. I guarantee that the group will listen. And if one person decides to be a DB and click need anyway, they have just alienated three players not just one.
Nah, this does not work in the current PUG situation, you can check the thousands of posts regarding this matter since launch.
In every groupfinder flashpoint I do I ask the team only to need on items they can use themselves, in most cases nobody answers. Communication is not the strongest part of most PUGs nowdays through groupfinder. Your guarantee that everyone listens is sadly not worth much since I know it is the opposite.
You canīt check every boss for every specific item and tell the team not to roll on it, you discover in almost all cases afterwards that someone has taken the item and then it is to late.
It is much better to have a common sense lootsystem where you can need roll on the items your class uses and restrict all other classes from needing it. Greed will be open for everyone to use and if someone wants it for a companion/sell it/give it to a alt/eat it the greed option is the best to use.
Anyways the players that wants to roll on every item will always argue that a better lootsystem is a bad idea, question is why