There are several problems with Paladins that people don't want to take them vs Warriors.

1. Low HP. A Paladin with their AF gear has a little over 3k hp while a warrior has over 4k. As a class where the only thing they can do is really tank they probably should have the highest HP in the game.

2. Area of Effect Damage and low overall damage. Paladins have very little ability to tank groups of mobs in a party situation. They have flash and war drum, but flash doesn't do damage and war drum does like 60 damage to each mob. Damage dealers will pull off mobs that you are not directly targeting. Warrior on the other hand has Steel Cyclone which hits all mobs in an area for 1500+ damage which allows warrior to keep solid hate on like 10+ monsters, and do insane amounts of damage. When you have raids that are time runs basically that means you can't take Paladin because their damage output isn't high enough.

3. Damage Taken I been told by white mages that Paladin or Warrior about the same when it comes to healing its not really harder to heal a Warrior vs a Paladin. Here a paladin could use more damage reduction.

4. Enmity Generation, other people can pull mobs from the Paladin, To make up for their lack of damage they should have some tanking stance which increases enmity generation. Again warrior has less of a problem with this given how much more damage they are doing it.

So in the end people just want warriors because they can do more damage and they do so much more damage and take about the same amount of damage. PLD could definitely use a AoE weapnskill, maybe make Spirits Within AoE. Wardrum defiantly needs a buff, like a 30 sec cooldown does like 500+ damage also take the block requirement off of it. That way AoE taking wouldn't be as much of an issue.

Basically Paladin needs, more AoE skills and damage to enemies, better enmity generation, and more damage mitigation, for people to actually want to take Paladins.