I have question?

[Kirika-]

Tanks and Healer jobs more often have lower queue times for Duty Finder, however one reason for that is it takes less tanks or healers to fill a Light or Full Party.
Each job in the game can solo all the solo content.
For Solo:

1. DPS = Damage the target faster than it damages you
2. Tank = Damage the target while absorbing and mitigating the damage directed to you
3. Healer = Damage the target while recovering the damage taken though self healing and shielding

DPS' kit generally makes soloing seem easier, as stuff seems to die faster, while Tanks and Healers seems to be slower/harder in solo content, which is why the DPS job is more popular, it's players are more numerous, and generally have to wait longer in queue, just because there are more of them in queue.
To help offset this, Light and Full Party Duty Finder make up has more than one DPS for each Tank and Healer slot. (Light = Tank, Healer, Two DPS - Full = Two Tanks, Two Healers, Four DPS')

That said, it is really up to you and how you want to play, but unlike a lot of other MMORPG games, you can be all three roles, as you can level every job in the game on one character and switch between them out of combat/duty's.