Paladin raid off-tanking

[JickFromTholuxe]

I've heard a few times that Paladins make good off-tanks at raids but I don't recall hearing reasons why that's the case. Are there reasons that make them better than warriors at off-tanking? In practice, do guilds that have an abundance of well-geared classes ever do this? I've only been on a few raids on P99 before but I do seem to recall seeing Paladins off-tanking. I don't know if this was because they lacked a warrior to do the job, if the Paladin happened to be better geared, or what.

Besides the Fiery Defender and resist gear, is there any gear that's indispensable for Paladin raiding?

Could anyone offer any other tips for a raiding Paladin? Thanks in advance.