Paladin has by far the best support healing of all tanks.
Yes, normally you don't use it but when you have to use it then you got the strongest single heal spell of all classes

Yes, he has no self-healing in his normal rotation but when something goes wrong then you have the PLD as 3rd healer.
And that is something I like about the class.
I can't count the amount of runs and further progress I've saved/ enabled just because I can full heal a DPS with 1 clemency from 10% to 100% while healing myself for a lot.

If it's needed PLD has the strongest healing of all tanks.