All 3 can hold enmity in dungeons easily, depending on the gap of gear strength between you and the party. The only time you'll have difficulty holding aggro, assuming your gear isn't falling too far behind, are the first few dungeons as you don't have your tank stance to help keep aggro.

In terms of rotation, PLD is very straightforward for tanking, they have a good amount of buffs and at later levels can heal themselves if needed.

But if you want something a bit more challenging to play there's WAR who have to make sure to keep up their damage buffs, and DRK who rely on spending and gaining MP to empower their moves.