I actually wouldn't mind seeing a unique mount for each job. Just because there's an abundance of DPS (and the number of DPS jobs far outnumber the number of Tank or Healer jobs) doesn't mean those jobs shouldn't get attention. A cosmetic on your mount to do 8-man content is no real incentive to be that particular role. However, the incredibly short queue-times are.
But yes, someone already pointed out the Unicorn for WHM. Though I don't look forward to the DRK flood when Expansion drops - though hopefully that'll phase out after a month, the people who play it because it looks cool or uses a zweihander. I've encountered enough Tanks that somehow make it to KotL through the cool factor of axes and/or swords and playing the game like it's a single-player game or that they're the only one that matters and everyone else is a NPC. My gawd the horror....