Another one I'd like to see is a more advanced LFG system that takes into account the fact that many if not most players have multiple characters (spread across one or more servers), of whom some are more fun to play solo whilst others are more fun to play in groups or raids.
Meaning, let players queue one toon (for a group role suited to that character), and then while you wait for your number to come up, you get to switch to a different toon to pass the time.
For example want to queue up your DPS for a pug or LFR, but don't feel like killing time on that toon for the next 10-30 minutes running solos or w/e? Fine, queue up your DPS and switch to your solo class; similar to how GM tickets cause a small icon to appear on any character you play, this queue does something similar, and when a group is found, you get the usual popup window - but when you click "accept", it switches you back to the queued toon before adding you to the group.
Having dual spec kind of offsets this, but only kinda - maybe I only *want* to play my DPS... as a DPS. Etc.
This is really a pretty simple idea and I'm sure it's far from unique, but unfortunately only seems to be implemented by smaller / newer / hungrier MMOs looking for an extra niche.