Basically if you are new to the level 50 tanking role, and you are trying to gear up, there is no way in hell you can hold threat on a geared BM or Summoner
You can just tell them "guys don't rush, i'm fresh 50" and thats it. PLD with GC weapon can easily hold aggro on relic-toting BLM, given a few seconds to raise threat. Even if you lose aggro after several hard nukes, mob will almost dead already.

People say titan hard mode is easiest on Paladin, while i felt that fight was ~insanely~ much much easier on monk.
How come? Tank job on Titan HM just "standing there", literally, and smack 1-2-3 till post-heart. Then add one defensive CD at start of the phase and after each Landslide.

The reason people dont play tank jobs is because most people lack the skill.
The only time some skill is really needed, its in high-end dungeons and Ex primals. But then everyone need skill, not just tanks.