well. imo it is not that difficult as long as you don't have a retard DD. normally when u focus on one target, it is fine. Even with srsly undergeared tank and full DL,relic+1 dps, heal in AK, it all depends on the skill of the tank and brains of the rest of the party, because some tanks can manage it and some don't, so...
Also there are so many other bonuses that helps tank if comparing to other MMOs as u are saying:
1) if u have a blm, they just have the most awesome cc with their mass sleep - problem here is that someone usually aoes them out of it
2) dds can have damage mitigating cross skills (i always keep 1 or 2 cross skill life savers on my bar) in case of emergency
3) dds are just not as squishy. usually tank has time to take back aggro because heal can actually keep even casters alive for quite some time.
the main thing in this game is actually cooperation in party and actions of every party member influences outcome greatly...
