Hasted PAM Vengeance Paladin after level 15 can already attack 5 times per turn his VoE target or 4 times his non-VoE target. If enemy closes distance first and PAM attack occure- that could potentially be 6 attacks per turn. Add 2 levels of Fighter and couple of levels of Sorc to not lose spell progress and you can with Action Surge and PAM Vengeance Paladin attack up to 8 times in one turn, smitting on each one.
It can already be done and it's not really that game-breaking.
As to Topic: I agree. Actually after playing Sorcadin Divine Soul and playing Divine Soul Sorlock who was support with Agonizing Blast as his DPR while his spells were mostly Cleric ones - I don't see a place for Clerics to do something those can't do (sure Turn Undead is cool, but it's very situational) and do better.
I think they should put Paladin and Cleric into one class, change it's name and make them subclasses.
But not before they fix Sorcerers.