In order to let paladin have a more potent cure (cure II as in your example) they woul probably have to be nerfed in mitignation to compensate, like loose out on some dmg reduction from of Shield Oath or similar change.
I'm pretty sure no one would be happy with that tradeoff, I sure wouldn't be.

Warrior is the tank class that is balanced around self healing, and even that isn't realy working out as well as in theory atm, and SE have already announced its being looked into.

Paladin tanks trough rotating defensive cooldowns and having extra damage reduction trough a self buff, if you want to "heal" yourself as a PLD then Stoneskin is a useable option for many figths, if not use your MP on casting Flash.