probably said already but i don't want to read through all replies zzzz
If an item has a low drop rate (Felstriker, Dal'rend(s), Ironfoe,) I think the person who puts the effort to form the group and finds someone with a key (if needed of course) should be able to reserve an item of whatever they want. If you need the item that's reserved, then don't go, others will fill your spot. Not everyone is going after the exact same loot. Besides, there are groups at nearly every time of the day doing dungeons; you're bound to find a group where the item you need isn't reserved. And, if you need that item that all the parties reserve, make your own group and reserve it for yourself.
And to the person who was saying that reserving items """ruins""" the fun from dungeons.. uh??? hello? It's not fun to do like 20-30 UBRS runs for your Dal'rends or like 100 for your Ironfoe/Felstriker only to lose them to some random.