I can see some changes that could be possible. Change Sword Oath to give 25% improvement on heals rather than dps and decrease dps by 25%.
Give them Cure II but remove hollowed ground and replace it with a buff to allow a cast to be uninterrupted so they can utilize cure II.
Since they gain an extra cross class ability need to remove something probably from conjurer however I would like to see them lose the warrior 20% defensive buff.

Now like a warrior can be used as a sub par dps when only 1 tank is needed the paladin can be used as a sub par healer when only 1 is needed.