Both of the tanks that are available from level 1 are easy to pick up and learn. They don't get that much harder going into the late game, either. If anything, the harder to learn tanks are probably DRK and GNB, with DRK being the one that is the most difficult to play due to having a lot of bloat in their kit. Gunbreaker is fun and sort of plays like a melee dps / tank hybrid, though it does have some rather interesting "clipping" issues on some skills.

I would say paladin is the more accurate tank experience in terms of survivability. Warrior is just broken for anything that isn't end game since the damage done in normal content is so low, that self healing without having to surrender any attacks makes them almost too good at their jobs. However, a lot of this depends on keeping gear up to date.