Let's slow down for a minute. Forget about leveling "speed"...

What do you want out of a class/job?

Do you want to feel powerful and make things die as fast as possible? DPS (And there are several flavors here.)
Do you want to protect the party, and lead and set the pace? Tank is the way to go.
Still protecting the party--keeping them vertical and getting them back on their feet when the worst happens? Healer, naturally.

There are nuances and flavors to each of these and maybe one of those takes priority over the categories I've listed above. But back to the question:

What do you want out of your class/job?